This diff checks if the fid stored in the synced metadata table store is still valid. We could run into this situation, if a user connects their facaster account to their comm account, then later deletes their farcaster account, but their comm account still has the old deleted fid. If this is the case we should unlink this fid from the user's comm account
Linear task: https://linear.app/comm/issue/ENG-7277/check-if-the-user-fid-stored-in-the-synced-metadata-table-is-still
Depends on D12569
It might look uncommon to have interface declaration and implementation next to each other in a single file but in fact we don't need to expose CommServicesAuthMetadataIOSWrapper. If we want to call sendAuthMetadataToJS from Objective - C we can use the common C++ API so let's avoid creating unnecessary files and duplication the same API.