Integration with Voyage (langchain4j#1816)

## Issue
Closes langchain4j#1814 and langchain4j#1813 

## Change
1. Integration `EmbeddingModel` and `ScoringModel` with `Voyage`.
2. Add document about `VoyageEmbeddingModel` and `VoyageScoringModel`

Related PR:

1. [Voyage
Example](langchain4j/langchain4j-examples#109)
2. [Voyage Spring
Boot](langchain4j/langchain4j-spring#42)

## General checklist
<!-- Please double-check the following points and mark them like this:
[X] -->
- [x] There are no breaking changes
- [x] I have added unit and integration tests for my change
- [x] I have manually run all the unit and integration tests in the
module I have added/changed, and they are all green
- [x] I have manually run all the unit and integration tests in the
[core](https://github.com/langchain4j/langchain4j/tree/main/langchain4j-core)
and
[main](https://github.com/langchain4j/langchain4j/tree/main/langchain4j)
modules, and they are all green
<!-- Before adding documentation and example(s) (below), please wait
until the PR is reviewed and approved. -->
- [x] I have added/updated the
[documentation](https://github.com/langchain4j/langchain4j/tree/main/docs/docs)
- [x] I have added an example in the [examples
repo](https://github.com/langchain4j/langchain4j-examples) (only for
"big" features)
- [x] I have added/updated [Spring Boot
starter(s)](https://github.com/langchain4j/langchain4j-spring) (if
applicable)

## Checklist for adding new model integration
<!-- Please double-check the following points and mark them like this:
[X] -->
- [x] I have added my new module in the
[BOM](https://github.com/langchain4j/langchain4j/blob/main/langchain4j-bom/pom.xml)

docs/docs/integrations/embedding-models/voyage-ai.md

@@ -0,0 +1,25 @@
+---
+sidebar_position: 4
+---
+
+# Voyage AI
+
+## Maven Dependency
+
+```xml
+<dependency>
+    <groupId>dev.langchain4j</groupId>
+    <artifactId>langchain4j-voyage-ai</artifactId>
+    <version>0.35.0</version>
+</dependency>
+```
+
+## APIs
+
+- `VoyageAiEmbeddingModel`
+
+
+## Examples
+
+- [VoyageAiEmbeddingModelIT](https://github.com/langchain4j/langchain4j/blob/main/langchain4j-voyage-ai/src/test/java/dev/langchain4j/model/voyageai/VoyageAiEmbeddingModelIT.java)
+- [VoyageAiEmbeddingModelExample](https://github.com/langchain4j/langchain4j-examples/blob/main/voyage-ai-examples/src/main/java/VoyageAiEmbeddingModelExample.java)

docs/docs/integrations/scoring-reranking-models/3-voyage-ai.md

@@ -0,0 +1,25 @@
+---
+sidebar_position: 2
+---
+
+# Voyage AI
+
+## Maven Dependency
+
+```xml
+<dependency>
+    <groupId>dev.langchain4j</groupId>
+    <artifactId>langchain4j-voyage-ai</artifactId>
+    <version>0.35.0</version>
+</dependency>
+```
+
+
+## Voyage AI Models
+
+- `VoyageAiScoringModel`
+
+
+## Examples
+- [Advanced RAG with re-ranking](https://github.com/langchain4j/langchain4j-examples/blob/main/rag-examples/src/main/java/_3_advanced/_03_Advanced_RAG_with_ReRanking_Example.java)
+- [VoyageAiScoringModelExample](https://github.com/langchain4j/langchain4j-examples/blob/main/voyage-ai-examples/src/main/java/VoyageAiScoringModelExample.java)

langchain4j-bom/pom.xml

@@ -171,6 +171,12 @@
                 <version>${project.version}</version>
             </dependency>
 
+            <dependency>
+                <groupId>dev.langchain4j</groupId>
+                <artifactId>langchain4j-voyage-ai</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+
             <!-- embedding stores -->
 
             <dependency>

langchain4j-voyage-ai/pom.xml

@@ -0,0 +1,113 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>dev.langchain4j</groupId>
+        <artifactId>langchain4j-parent</artifactId>
+        <version>0.35.0-SNAPSHOT</version>
+        <relativePath>../langchain4j-parent/pom.xml</relativePath>
+    </parent>
+
+    <artifactId>langchain4j-voyage-ai</artifactId>
+    <name>LangChain4j :: Integration :: Voyage AI</name>
+
+    <dependencies>
+        <dependency>
+            <groupId>dev.langchain4j</groupId>
+            <artifactId>langchain4j-core</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.squareup.retrofit2</groupId>
+            <artifactId>retrofit</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.squareup.retrofit2</groupId>
+            <artifactId>converter-jackson</artifactId>
+        </dependency>
+
+        <!-- DEPENDENCY CONFLICT RESOLUTION FOR OKHTTP (START) -->
+        <dependency>
+            <groupId>com.squareup.okhttp3</groupId>
+            <artifactId>okhttp</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-stdlib-jdk8</artifactId>
+        </dependency>
+        <!-- DEPENDENCY CONFLICT RESOLUTION FOR OKHTTP (END)  -->
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-junit-jupiter</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.tinylog</groupId>
+            <artifactId>tinylog-impl</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.tinylog</groupId>
+            <artifactId>slf4j-tinylog</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-enforcer-plugin</artifactId>
+                    <version>3.5.0</version>
+                    <executions>
+                        <execution>
+                            <id>enforce</id>
+                            <configuration>
+                                <rules>
+                                    <dependencyConvergence/>
+                                </rules>
+                            </configuration>
+                            <goals>
+                                <goal>enforce</goal>
+                            </goals>
+                        </execution>
+                    </executions>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
+
+</project>

langchain4j-voyage-ai/src/main/java/dev/langchain4j/model/voyageai/EmbeddingRequest.java

@@ -0,0 +1,85 @@
+package dev.langchain4j.model.voyageai;
+
+import java.util.List;
+
+class EmbeddingRequest {
+
+    private List<String> input;
+    private String model;
+    private String inputType;
+    private Boolean truncation;
+    private String encodingFormat;
+
+    EmbeddingRequest() {
+    }
+
+    EmbeddingRequest(List<String> input, String model, String inputType, Boolean truncation, String encodingFormat) {
+        this.input = input;
+        this.model = model;
+        this.inputType = inputType;
+        this.truncation = truncation;
+        this.encodingFormat = encodingFormat;
+    }
+
+    public List<String> getInput() {
+        return input;
+    }
+
+    public String getModel() {
+        return model;
+    }
+
+    public String getInputType() {
+        return inputType;
+    }
+
+    public Boolean getTruncation() {
+        return truncation;
+    }
+
+    public String getEncodingFormat() {
+        return encodingFormat;
+    }
+
+    static Builder builder() {
+        return new Builder();
+    }
+
+    static class Builder {
+
+        private List<String> input;
+        private String model;
+        private String inputType;
+        private Boolean truncation;
+        private String encodingFormat;
+
+        Builder input(List<String> input) {
+            this.input = input;
+            return this;
+        }
+
+        Builder model(String model) {
+            this.model = model;
+            return this;
+        }
+
+        Builder inputType(String inputType) {
+            this.inputType = inputType;
+            return this;
+        }
+
+        Builder truncation(Boolean truncation) {
+            this.truncation = truncation;
+            return this;
+        }
+
+        Builder encodingFormat(String encodingFormat) {
+            this.encodingFormat = encodingFormat;
+            return this;
+        }
+
+        EmbeddingRequest build() {
+            return new EmbeddingRequest(input, model, inputType, truncation, encodingFormat);
+        }
+    }
+}

langchain4j-voyage-ai/src/main/java/dev/langchain4j/model/voyageai/EmbeddingResponse.java

@@ -0,0 +1,58 @@
+package dev.langchain4j.model.voyageai;
+
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+
+import java.util.List;
+
+class EmbeddingResponse {
+
+    private String object;
+    @JsonDeserialize(using = VoyageAiEmbeddingDeserializer.class)
+    private List<EmbeddingData> data;
+    private String model;
+    private TokenUsage usage;
+
+    public String getObject() {
+        return object;
+    }
+
+    public List<EmbeddingData> getData() {
+        return data;
+    }
+
+    public String getModel() {
+        return model;
+    }
+
+    public TokenUsage getUsage() {
+        return usage;
+    }
+
+    static class EmbeddingData {
+
+        private String object;
+        private List<Float> embedding;
+        private Integer index;
+
+        EmbeddingData() {
+        }
+
+        EmbeddingData(String object, List<Float> embedding, Integer index) {
+            this.object = object;
+            this.embedding = embedding;
+            this.index = index;
+        }
+
+        public String getObject() {
+            return object;
+        }
+
+        public List<Float> getEmbedding() {
+            return embedding;
+        }
+
+        public Integer getIndex() {
+            return index;
+        }
+    }
+}