Changing messaging for ILlegalArgumentException on duplicate model gr… (#1294) (#1300)

* Changing messaging for ILlegalArgumentException on duplicate model group creation.

Signed-off-by: Nate Boot <[email protected]>

* Adjusting the test. `./gradlew test` passes.

Signed-off-by: Nate Boot <[email protected]>

---------

Signed-off-by: Nate Boot <[email protected]>
(cherry picked from commit a9687fc)

Co-authored-by: Nate B <[email protected]>

Author: opensearch-trigger-bot[bot]

plugin/src/main/java/org/opensearch/ml/model/MLModelGroupManager.java

@@ -75,11 +75,7 @@ public void createModelGroup(MLRegisterModelGroupInput input, ActionListener<Str
                             listener
                                 .onFailure(
                                     new IllegalArgumentException(
-                                        "The name you provided is already being used by another model with ID: "
-                                            + id
-                                            + ". Please provide a different name or add \"model_group_id\": \""
-                                            + id
-                                            + "\" to request body"
+                                        "The name you provided is already being used by a model group with ID: " + id + "."
                                     )
                                 );
                         }

plugin/src/test/java/org/opensearch/ml/model/MLModelGroupManagerTests.java

@@ -143,7 +143,7 @@ public void test_ModelGroupNameNotUnique() throws IOException {//
         ArgumentCaptor<Exception> argumentCaptor = ArgumentCaptor.forClass(Exception.class);
         verify(actionListener).onFailure(argumentCaptor.capture());
         assertEquals(
-            "The name you provided is already being used by another model with ID: model_group_ID. Please provide a different name or add \"model_group_id\": \"model_group_ID\" to request body",
+            "The name you provided is already being used by a model group with ID: model_group_ID.",
             argumentCaptor.getValue().getMessage()
         );