Backend: Get and Post endpoints text annotation by post-slug

Description:

We need to provide endpoints for the given post because when frontend needs a list of annotations for the given post. Get endpoints returns a list of annotations. Post endpoint creates an annotation for the given post. The body requiered to create is as follows:

{
    "position": {
        "start": 31,
        "end": 57
        },
      "data": {
        "text": "jjjjjjj",
        "source": "http://example.org/post-slug1313"
      }
}

Deadline: 25.12.2022 18.00

bounswe / bounswe2022group4

Backend: Get and Post endpoints text annotation by post-slug #550