This includes a new identity struct with a farcaster id field which we refactor get_user_identifier to return. This follows discussion from
https://linear.app/comm/issue/ENG-7759/modify-finduseridentity-to-take-list-of-userids-and-include-fid.
Depends on D11859
I introduced a previous diff where setAuxUserFIDs now clears fids prior to updating with new fids from the payload. The previous functionality of setAuxUserFIDs of just adding without clearing is now a new action type addAuxUserFIDs
There are now two callbacks which are called by a single useEffect. The two callbacks are called handleFarcasterMutuals and handleUserStoreFIDs