API.md: Document print_label.

API.md

@@ -59,6 +59,8 @@ The API is REST-like (but not entirely).
  * `PATCH /users/%uid%.json` - the same as above, but in JSON format (What's the difference?)
  * `DELETE /users/%uid%` - deletes the user with the id `%uid%`
  * `DELETE /users/%uid%.json` - the same as above, but in JSON format (What's the difference?)
+ * `POST /users/%uid%/print_label` - prints a label with the username and the current date
+ * `POST /users/%uid%/print_label.json` - the same as above, but in JSON format
  * `GET /users/%uid%/deposit?amount=%amount%` - adds the amount `%amount%` (in €) to the balance of the user with the id `%uid%` (**This GET request modifys data!**)
  * `GET /users/%uid%/deposit.json?amount%amount%` - the same as above, but in JSON format (What's the difference?) (**This GET request modifys data!**)
  * `GET /users/%uid%/pay?amount=%amount%` - removes the amount `%amount%` (in €) from the balance of the user with the id `%uid%` (**This GET request modifys data!**)