Ensure all properties are copied when converting to a2a

Python and Go implementations of ADK both copy function call and
response properties by copying the entire struct automatically. Java
does this a property at a time and so was missing the "id" property of
the ADK event. Providing these allows downstream agents to properly
associate multiple tool calls and responses to the same tool name.

Updated EventConverterTest to verify the new field and also verified
function name in the response object.

Author: zbirkenbuel

a2a/src/main/java/com/google/adk/a2a/converters/PartConverter.java

@@ -132,21 +132,32 @@ private static Optional<com.google.genai.types.Part> convertDataPartToGenAiPart(
     if (data.containsKey("name") && data.containsKey("args")
         || A2A_DATA_PART_METADATA_TYPE_FUNCTION_CALL.equals(metadataType)) {
       String functionName = String.valueOf(data.getOrDefault("name", ""));
+      String functionId = String.valueOf(data.getOrDefault("id", ""));
       Map<String, Object> args = coerceToMap(data.get("args"));
       return Optional.of(
           com.google.genai.types.Part.builder()
-              .functionCall(FunctionCall.builder().name(functionName).args(args).build())
+              .functionCall(
+                  FunctionCall.builder()
+                      .name(functionName)
+                      .id(functionId)
+                      .args(args)
+                      .build())
               .build());
     }
 
     if (data.containsKey("name") && data.containsKey("response")
         || A2A_DATA_PART_METADATA_TYPE_FUNCTION_RESPONSE.equals(metadataType)) {
       String functionName = String.valueOf(data.getOrDefault("name", ""));
+      String functionId = String.valueOf(data.getOrDefault("id", ""));
       Map<String, Object> response = coerceToMap(data.get("response"));
       return Optional.of(
           com.google.genai.types.Part.builder()
               .functionResponse(
-                  FunctionResponse.builder().name(functionName).response(response).build())
+                  FunctionResponse.builder()
+                      .name(functionName)
+                      .id(functionId)
+                      .response(response)
+                      .build())
               .build());
     }
 
@@ -167,6 +178,7 @@ private static Optional<com.google.genai.types.Part> convertDataPartToGenAiPart(
   private static Optional<DataPart> createDataPartFromFunctionCall(FunctionCall functionCall) {
     Map<String, Object> data = new HashMap<>();
     data.put("name", functionCall.name().orElse(""));
+    data.put("id", functionCall.id().orElse(""));
     data.put("args", functionCall.args().orElse(Map.of()));
 
     Map<String, Object> metadata =
@@ -185,6 +197,7 @@ private static Optional<DataPart> createDataPartFromFunctionResponse(
       FunctionResponse functionResponse) {
     Map<String, Object> data = new HashMap<>();
     data.put("name", functionResponse.name().orElse(""));
+    data.put("id", functionResponse.id().orElse(""));
     data.put("response", functionResponse.response().orElse(Map.of()));
 
     Map<String, Object> metadata =

a2a/src/test/java/com/google/adk/a2a/EventConverterTest.java

@@ -43,7 +43,12 @@ public void convertEventsToA2AMessage_preservesFunctionCallAndResponseParts() {
 
     Part functionCallPart =
         Part.builder()
-            .functionCall(FunctionCall.builder().name("roll_die").args(Map.of("sides", 6)).build())
+            .functionCall(
+                FunctionCall.builder()
+                    .name("roll_die")
+                    .id("adk-call-1")
+                    .args(Map.of("sides", 6))
+                    .build())
             .build();
     Event callEvent =
         Event.builder()
@@ -59,7 +64,11 @@ public void convertEventsToA2AMessage_preservesFunctionCallAndResponseParts() {
     Part functionResponsePart =
         Part.builder()
             .functionResponse(
-                FunctionResponse.builder().name("roll_die").response(Map.of("result", 3)).build())
+                FunctionResponse.builder()
+                    .name("roll_die")
+                    .id("adk-call-1")
+                    .response(Map.of("result", 3))
+                    .build())
             .build();
     Event responseEvent =
         Event.builder()
@@ -106,11 +115,14 @@ public void convertEventsToA2AMessage_preservesFunctionCallAndResponseParts() {
     assertThat(callDataPart.getMetadata().get(PartConverter.A2A_DATA_PART_METADATA_TYPE_KEY))
         .isEqualTo(PartConverter.A2A_DATA_PART_METADATA_TYPE_FUNCTION_CALL);
     assertThat(callDataPart.getData()).containsEntry("name", "roll_die");
+    assertThat(callDataPart.getData()).containsEntry("id", "adk-call-1");
     assertThat(callDataPart.getData()).containsEntry("args", Map.of("sides", 6));
 
     DataPart responseDataPart = (DataPart) message.getParts().get(2);
     assertThat(responseDataPart.getMetadata().get(PartConverter.A2A_DATA_PART_METADATA_TYPE_KEY))
         .isEqualTo(PartConverter.A2A_DATA_PART_METADATA_TYPE_FUNCTION_RESPONSE);
+    assertThat(responseDataPart.getData()).containsEntry("name", "roll_die");
+    assertThat(responseDataPart.getData()).containsEntry("id", "adk-call-1");
     assertThat(responseDataPart.getData()).containsEntry("response", Map.of("result", 3));
   }