Create internal-only classifier for Dataflow SDK

This creates a valid module which the worker package
can depend on so it can share Guava objects between
itself and the SDK module until the worker package
is fully separated.

Users should not depend on this classifier as
it will be removed.

This is towards ASF Beam.

----Release Notes----

[]
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=113593122

Author: lukecwik

sdk/pom.xml

@@ -289,7 +289,24 @@
         <artifactId>maven-shade-plugin</artifactId>
         <version>2.3</version>
         <executions>
-          <!-- In the first phase, we pick dependencies and relocate them. -->
+          <!-- In the first phase, we create a special classifier for a
+               jar with no relocations. This classifier should not
+               be depended on as it is considered deprecated and will
+               be removed. TODO: Remove once worker module does not
+               share Guava dependency. -->
+          <execution>
+            <id>internal-only</id>
+            <phase>package</phase>
+            <goals>
+              <goal>shade</goal>
+            </goals>
+            <configuration>
+              <shadedArtifactAttached>true</shadedArtifactAttached>
+              <shadedClassifierName>internal-only</shadedClassifierName>
+            </configuration>
+          </execution>
+
+          <!-- In the second phase, we pick dependencies and relocate them. -->
           <execution>
             <id>bundle-and-repackage</id>
             <phase>package</phase>
@@ -329,7 +346,7 @@
             </configuration>
           </execution>
 
-          <!-- In the second phase, we pick remaining dependencies and bundle
+          <!-- In the third phase, we pick remaining dependencies and bundle
                them without repackaging. -->
           <execution>
             <id>bundle-rest-without-repackaging</id>

worker/pom.xml

@@ -209,6 +209,7 @@
       <groupId>com.google.cloud.dataflow</groupId>
       <artifactId>google-cloud-dataflow-java-sdk-all</artifactId>
       <version>${project.version}</version>
+      <classifier>internal-only</classifier>
     </dependency>
 
     <!-- test dependencies -->