Add versionid header in complete multipart if enabled (#3643)

* Add versionid header in complete multipart if enabled
- addresses https://github.com/localstack/localstack/issues/3514

* remove unnecessary code

* fix lint

* fix lint test

* add test case for boto3

moto/s3/responses.py

@@ -1750,8 +1750,15 @@ class ResponseObject(_TemplateEnvironmentMixin, ActionAuthenticatorMixin):
             upload_id = query["uploadId"][0]
             key = self.backend.complete_multipart(bucket_name, upload_id, body)
             template = self.response_template(S3_MULTIPART_COMPLETE_RESPONSE)
-            return template.render(
-                bucket_name=bucket_name, key_name=key.name, etag=key.etag
+            headers = {}
+            if key.version_id:
+                headers["x-amz-version-id"] = key.version_id
+            return (
+                200,
+                headers,
+                template.render(
+                    bucket_name=bucket_name, key_name=key.name, etag=key.etag
+                ),
             )
         elif "restore" in query:
             es = minidom.parseString(body).getElementsByTagName("Days")