Update post add/update/delete

PROPOSAL:
- { "mark_as_read": 1 }                    ... value is ment to be singular and only one value should exist
- { "colours": ["red", "green", "blue"] }  ... any other colours should be removed and only RGB is ment to remain
- { "colours": null }                      ... destroys all values
- { "colours": [] }                        ... destroys all values