Extend API get bucket

[astsiapanay]

Extend the GET /v1/bucket response with an additional field - appdata field.
If the GET /v1/bucket request is done with a Per-request key the response will contain appdata field with the path to the shared application folder, including the User's bucket and the correct deployment-id for the application as registered in the Core configs.

GET /v1/bucket
{
  "bucket": "{application-bucket-id}",
  "appdata": "files/{user-bucket-id}/appdata/{deployment-id}",
}

[astsiapanay]

resolved by #131