Background
The Unblock API currently assumes $wgEnableMultiBlocks is false, and provides no means to remove a specific block.
For the Block API, see T378147
Acceptance criteria
- Use the existing id parameter to support block ID, which tells the backend to remove only that block
- If both an id and username are provided, error out with a detailed message - "you should only provide username OR id, not both"
- If no id is provided and a user is provided, remove all blocks for that user (this is the current behaviour)