STUFF

WOOT:
  - How to handle this case (different relationship resource type/name (author != people)):
  POST /articles/1/links/author
  {
    "people": "12"
  }
  => Resource type and name are two different things !

  - How to handle HABTM vs regular to_many ?

WARNING: Ruby code for illustration purposes, NOT CORRECTNESS

CREATE RESOURCE:
  POST /albums
  {
    albums: {
      title: "Animals"
    }
  }
  Album.new(title: 'Animals').save!
  INSERT INTO `albums` (`title`) VALUES ('Animals');

DELETE RESOURCE:
  DELETE /albums/1
  album = Album.find(1)
  album.destroy
  DELETE FROM `album` WHERE `album`.`id` = 1

GET TO_ONE RELATIONSHIP:
  GET /albums/1/links/band
  album = Album.find(1)
  album.band
  SELECT `albums`.* FROM `albums`  WHERE `albums`.`id` = 1 LIMIT 1;
  SELECT `bands`.* FROM `bands`  WHERE `bands`.`id` = #{album.band_id} LIMIT 1;

CREATE/REPLACE TO_ONE RELATIONSHIP:
  POST /albums/1/links/band
  {
    bands: "2"
  }
  album = Album.find(1)
  album.band = Band.find(2)
  UPDATE `albums` SET `band_id` = 2 WHERE `albums`.`id` = 1

REPLACE TO_ONE RELATIONSHIP (equivalent to ADD/REPLACE above):
  PUT /albums/1
  {
    "articles": {
      "can_update_other_properties_too": true,
      "links": {
        "band": "42"
      }
    }
  }
  album = Album.find(1)
  album.update_attributes(attr)
  album.band = Band.find(42)
  UPDATE `albums` SET `attr` = attr WHERE `albums`.`id` = 1
  UPDATE `albums` SET `band_id` = 42 WHERE `albums`.`id` = 1

DELETE TO_ONE RELATIONSHIP:
  DELETE /albums/1/links/band
  album = Album.find(1)
  album.band = nil (.clear instead ?)
  UPDATE `albums` SET `band_id` = NULL WHERE `albums`.`id` = 1

GET TO_MANY RELATIONSHIP:
  GET /albums/1/links/tracks
  album = Album.find(1)
  album.tracks
  SELECT `tracks`.* FROM `tracks`  WHERE `tracks`.`album_id` = 1;

CREATE/ADD TO_MANY RELATIONSHIPS:
  POST /album/1/links/tracks
  {
    tracks: ['1', '2']
  }
  album = Album.find(1)
  album.tracks << tracks
  UPDATE `tracks` SET `album_id` = 1 WHERE `tracks`.`id` = 1
  UPDATE `tracks` SET `album_id` = 1 WHERE `tracks`.`id` = 2

REPLACE TO_MANY RELATIONSHIP (equivalent to ADD/REPLACE above):
  PUT /albums/1
  {
    "articles": {
      "can_update_other_properties_too": true,
      "links": {
        // This can be an empty array (remove all)
        "tracks": ["3", "5"]
      }
    }
  }
  album = Album.find(1)
  album.update_attributes(attr)
  album.tracks = tracks
  UPDATE `tracks` SET `tracks`.`album_id` = NULL WHERE `tracks`.`album_id` = 1 AND `tracks`.`id` IN (#{previous_track_ids})
  UPDATE `tracks` SET `album_id` = 1 WHERE `tracks`.`id` = 3
  UPDATE `tracks` SET `album_id` = 1 WHERE `tracks`.`id` = 5 

DELETE TO_MANY RELATIONSHIPS:
  DELETE /albums/1/links/tracks/3,4
  album = Album.find(1)
  album.tracks.where(id: [3, 4]).destroy_all
  UPDATE `blog_post_pictures` SET `blog_post_pictures`.`post_id` = NULL WHERE `blog_post_pictures`.`id` IN (3, 4)