Added test file.
Handled method not allowed.
Added test on empty username.
Handled empty username and room_id parameters.
Added test on empty room id.
Added test on username and room_id not set as parameter.
Handled not found room and not found user.
Added test on not found room and not found user.
Handled leaving the room of the creator.
Added test when creator wants to leave.
Added test when member wants to elave.
Added test if member wants to leave.
Added test if member wants to leave.
Resolved merge conflict.
Merge branch 'leave-room-handler-tests' into development