chore(internal): add and tweak check functions

increase-java-core/src/main/kotlin/com/increase/api/core/Check.kt

@@ -4,4 +4,27 @@ package com.increase.api.core
 
 @JvmSynthetic
 internal fun <T : Any> checkRequired(name: String, value: T?): T =
-    checkNotNull(value) { "`$name` is required but was not set" }
+    checkNotNull(value) { "`$name` is required, but was not set" }
+
+@JvmSynthetic
+internal fun checkLength(name: String, value: String, length: Int): String =
+    value.also {
+        check(it.length == length) { "`$name` must have length $length, but was ${it.length}" }
+    }
+
+@JvmSynthetic
+internal fun checkMinLength(name: String, value: String, minLength: Int): String =
+    value.also {
+        check(it.length >= minLength) {
+            if (minLength == 1) "`$name` must be non-empty, but was empty"
+            else "`$name` must have at least length $minLength, but was ${it.length}"
+        }
+    }
+
+@JvmSynthetic
+internal fun checkMaxLength(name: String, value: String, maxLength: Int): String =
+    value.also {
+        check(it.length <= maxLength) {
+            "`$name` must have at most length $maxLength, but was ${it.length}"
+        }
+    }

increase-java-core/src/main/kotlin/com/increase/api/core/ClientOptions.kt

@@ -173,8 +173,8 @@ private constructor(
         }
 
         fun build(): ClientOptions {
-            checkRequired("httpClient", httpClient)
-            checkRequired("apiKey", apiKey)
+            val httpClient = checkRequired("httpClient", httpClient)
+            val apiKey = checkRequired("apiKey", apiKey)
 
             val headers = Headers.builder()
             val queryParams = QueryParams.builder()
@@ -185,7 +185,7 @@ private constructor(
             headers.put("X-Stainless-Package-Version", getPackageVersion())
             headers.put("X-Stainless-Runtime", "JRE")
             headers.put("X-Stainless-Runtime-Version", getJavaVersion())
-            apiKey?.let {
+            apiKey.let {
                 if (!it.isEmpty()) {
                     headers.put("Authorization", "Bearer $it")
                 }
@@ -194,10 +194,10 @@ private constructor(
             queryParams.replaceAll(this.queryParams.build())
 
             return ClientOptions(
-                httpClient!!,
+                httpClient,
                 PhantomReachableClosingHttpClient(
                     RetryingHttpClient.builder()
-                        .httpClient(httpClient!!)
+                        .httpClient(httpClient)
                         .clock(clock)
                         .maxRetries(maxRetries)
                         .idempotencyHeader("Idempotency-Key")
@@ -210,7 +210,7 @@ private constructor(
                 queryParams.build(),
                 responseValidation,
                 maxRetries,
-                apiKey!!,
+                apiKey,
                 webhookSecret,
             )
         }

increase-java-core/src/main/kotlin/com/increase/api/core/Values.kt

@@ -117,6 +117,8 @@ sealed class JsonField<out T : Any> {
             is JsonValue -> this
         }
 
+    @JvmSynthetic fun accept(consume: (T) -> Unit) = asKnown().ifPresent(consume)
+
     fun <R> accept(visitor: Visitor<T, R>): R =
         when (this) {
             is KnownValue -> visitor.visitKnown(value)