Add Beta annotation, modify access on deserializer, improve test

- make PolymorphicFallbackDeserializer AllArgsConstructor protected and use chaining
- Add beta annotation to MultiChatMessageContent and ChatMessagesInner
- move request body constraint to stub

Author: rpanackal

orchestration/src/main/java/com/sap/ai/sdk/orchestration/model/ChatMessagesInner.java

@@ -14,11 +14,13 @@
 
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.google.common.annotations.Beta;
 
 /** ChatMessagesInner */
 @JsonTypeInfo(use = JsonTypeInfo.Id.DEDUCTION)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = ChatMessage.class),
   @JsonSubTypes.Type(value = MultiChatMessage.class),
 })
+@Beta
 public interface ChatMessagesInner {}

orchestration/src/main/java/com/sap/ai/sdk/orchestration/model/MultiChatMessageContent.java

@@ -14,11 +14,13 @@
 
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.google.common.annotations.Beta;
 
 /** MultiChatMessageContent */
 @JsonTypeInfo(use = JsonTypeInfo.Id.DEDUCTION)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = ImageContent.class),
   @JsonSubTypes.Type(value = TextContent.class),
 })
+@Beta
 public interface MultiChatMessageContent {}

orchestration/src/test/java/com/sap/ai/sdk/orchestration/OrchestrationUnitTest.java

@@ -646,8 +646,11 @@ void streamChatCompletionDeltas() throws IOException {
   @Test
   void testRequestWithMultiChatMessage() throws IOException {
 
+    var expectedJsonRequest =
+        new String(fileLoader.apply("multiChatMessageRequest.json").readAllBytes());
     stubFor(
         post("/completion")
+            .withRequestBody(equalToJson(expectedJsonRequest, true, false))
             .willReturn(
                 aResponse().withStatus(SC_OK).withBodyFile("multiChatMessageResponse.json")));
 
@@ -739,12 +742,7 @@ void testRequestWithMultiChatMessage() throws IOException {
     assertThat(orchestrationResult.getUsage().getPromptTokens()).isEqualTo(928);
     assertThat(orchestrationResult.getUsage().getTotalTokens()).isEqualTo(959);
 
-    try (var requestInputStream = fileLoader.apply("multiChatMessageRequest.json")) {
-      final String requestBody = new String(requestInputStream.readAllBytes());
-      verify(
-          postRequestedFor(urlPathEqualTo("/completion"))
-              .withRequestBody(equalToJson(requestBody)));
-    }
+    verify(postRequestedFor(urlPathEqualTo("/completion")));
   }
 
   @SneakyThrows