Replace `foreignkey` with embedded object rather than having both.

[drizzle042]

This would save the extra bytes of memory required to keep both keys. Since embedded object's id is equivalent to foreignkey, we can do away with the foreignkey and save those extra bytes.

Current behaviour:

Before _embed:

{
  "employees": [
    { "id": 0, "name": "Tim", "lastName": "S", "role": "developer" }
  ],
  "feedbacks": [
    { "id": 0, "employeeId": 0, "text": "Great dev"}
  ]
}

After _embed:

[
  {
    "id": 0,
    "employeeId": 0,
    "text": "Great dev",
    "employee": {
      "id": 0,
      "name": "Tim",
      "lastName": "S",
      "role": "developer"
    }
  }
]

Expected behaviour:

Before _embed:

{
  "employees": [
    { "id": 0, "name": "Tim", "lastName": "S", "role": "developer" }
  ],
  "feedbacks": [
    { "id": 0, "employeeId": 0, "text": "Great dev"}
  ]
}

After _embed:

[
  {
    "id": 0,
    "text": "Great dev",
    "employee": {
      "id": 0,
      "name": "Tim",
      "lastName": "S",
      "role": "developer"
    }
  }
]

Might not seem like much but it will really save a lot in network data transfer.