[WIP] Implement external interactions

[oxnr]

Implement Comments and Likes on external objects in SDK.

API

We going to provide a new set of routes which at their roots share /externals and offer the same functionality that can be found for /posts. Instead of expecting a post id we offer a that a set of alphanumeric characters can be passed which is used to associate the entity created with it for later reference and list retrieval.

/externals/{externalID:[a-zA-Z0-9]+}/comments
/externals/{externalID:[a-zA-Z0-9]+}/likes
...

To offer the same convenience that we have for Posts (e.g. Counts) for external objects we going to serve a limited response for /externals/:id.

"counts": {
  "comments": 3,
  "likes": 12,
  "shares": 1
},
"id": "1a2b7c4d3e6f3g1h3i0j3k6l4m7n8o3p9q"

Another assumption which doesn't hold true is the knowledge around Visibility which means that we have to force the caller to provide that information.

curl -X POST /externals/1a2b7c4d3e6f3g1h3i0j3k6l4m7n8o3p9q/comments \
    -d $'
    {
        "content": "Do like.",
        "visibility": 30
    }
    '

201 Created
{
  "content": "Do like.",
  "external_id": "1a2b7c4d3e6f3g1h3i0j3k6l4m7n8o3p9q",
  "id": "12743631303647840",
  "user_id": "11286878691041888",
  "visibility": 30,
  "created_at": "2015-11-27T16:03:36.171840385Z",
  "updated_at": "2015-11-27T16:03:36.171840478Z"
}

curl -X POST /externals/1a2b7c4d3e6f3g1h3i0j3k6l4m7n8o3p9q/like \
    -d $'
    {
      "visibility": 30
    }
    '

201 Created
{
  "external_id": "1a2b7c4d3e6f3g1h3i0j3k6l4m7n8o3p9q",
  "id": "37363583381716140",
  "user_id": "11286878691041888",
  "created_at":"2015-03-21T14:28:02.4+01:00",
  "updated_at":"2015-03-21T14:28:02.4+01:00"
}