As we changed the messages table model to use a composite key in ENG-1362 we can use a composite key instead of an index in `findMessageItem`, `removeMessageItem` methods to improve database lookup performance.
Linear task: [[ https://linear.app/comm/issue/ENG-1493/change-findmessageitem-removemessageitem-to-use-composite-key | ENG-1493 ]]