Add tests for submitting meta

[bkoelman]

There is no test coverage for sending meta in request bodies.

For example:

POST /api/people HTTP/1.1

{
  "data": {
    "type": "people",
    "attributes": {
      "firstName": "John",
      "lastName": "Doe"
    }
  },
  "meta": {
    "root": {
      "child": {
        "key-A": "value-A",
        "key-B": "value-B"
      }
    }
  }
}

[Jeeva7RP-DevEng]

Hi @bkoelman Can I work on this issue!, I am very beginner to open contribute if, I can work on this issue can u please give me more details

[bkoelman]

Hello @Jeeva7RP-DevEng, thanks for offering your help.

I've added the basic boilerplate to get you started in cd9fa50. It contains a TODO comment to give some ideas on what to test. To set up your local development environment, see https://github.com/json-api-dotnet/JsonApiDotNetCore?tab=readme-ov-file#development.

I'm about to go on vacation, so I won't be able to respond for the next two weeks.