Merge pull request #3651 from aws/adaines/fix-RestJsonEnumPayloadRequest-protocol-test

fix: Improve enum payload handling in JSON RPC and REST JSON protocols

Author: AlexDaines

generator/.DevConfigs/ddb8a486-241f-48ce-b75f-3752d5171320.json

@@ -0,0 +1,9 @@
+{
+    "core": {
+      "changeLogMessages": [
+        "Fixed JsonRPCRequestMarshaller to properly handle enum payloads by setting content headers to plain text instead of JSON object"
+      ],
+      "type": "patch",
+      "updateMinimum": true
+    }
+  }

generator/ProtocolTestsGenerator/smithy-dotnet-codegen/src/main/java/software/amazon/smithy/dotnet/codegen/customizations/ProtocolTestCustomizations.java

@@ -109,7 +109,6 @@ private ProtocolTestCustomizations() {
             "QueryQueryFlattenedXmlMapWithXmlNamespace",
             "RestXmlXmlMapWithXmlNamespace",
             //These are the tests that are failing in v4 after updating to 1.54.0 and artifacts 1.0.3004.0. Each one needs to be investigated.
-            "RestJsonEnumPayloadRequest",
             "RestJsonStringPayloadRequest",
             "RestJsonNullAndEmptyHeaders",
             "RestJsonSerializesSparseNullMapValues",