Add a way for JSON requests to specify the format

[Eldelshell]

The idea is to allow different JSON formats which can be used with different REST clients.

The default format is:

{
  "success":true,
  "status":"OK",
  "rows":[
    {
      "roi":0,
      "cells":{
        "birthday":"1982-12-13",
        "name":"foo",
        "id":0,
        "lastupdate":"2020-05-08T21:17:21.993+02:00",
        "credit":32.50,
        "age":30
      }
    }
  ],
  "resource":"users",
  "pagination":{
    "page":1,
    "size":6,
    "pages":1,
    "total":6
  }
}

To allow this, we can either use:

• a map JSON file set with configuration
• During runtime with a POST endpoint which receives the format JSON data.
• Allow GET endpoints to accept POST requests with the format JSON data.

The format data would look like:

{
  "formats": [
    {
      "resource": "users",
      "meta": {
        "success": true,
        "status": false,
        "pagination": true
      },
      "model": {
        "id": "number",
        "name": "string",
        "birthday": "dd/MM/yyyy",
        "credit": "number"
      }
    },{
      "resource": "cars",
      "meta": null,
      "model": {
        "id": "number",
        "maker": "string",
        "lastUpdate": "ddMMyyyyhhmmss"
      }
    }
  ]
}

A response from users then would be formatted as:

{
  "success":true,
  "pagination":{
    "page":1,
    "size":6,
    "pages":1,
    "total":6
  },
  "entities": [
    {
      "id":0,
      "name":"foo",
      "birthday":"13/12/1982",
      "credit":32.50
    }
  ]
}

And a response from cars (with no metadata) would look like:

{
  "id":0,
  "maker":"foo",
  "lastUpdate":"13121982040130"
}

[Eldelshell]

It might be also be possible to set "meta": "head" so the pagination is received as HTTP headers.