Need to POST simple string data

[kavics]

The ODataRequest's PostData accepts any object that will be JSON-serialized to a string. For example: { "Name": "value" }. In some cases, it needs to post a simple string but the post-data will also be JSON-serialized:
Initial data: models=[{"a"=1,"b"=2}] but it sent as "models=[{\"a\"=1,\"b\"=2}]"
Expectation: Do not serialize the OdataRequest.PostData if its value is a string.