Mute / Unmute functionality
BE doesn't support mutes as of the moment, even for MastodonAPI endpoints we do return unmodified relation between blocker and blockee:
post("/accounts/:id/mute", MastodonAPIController, :relationship_noop)
post("/accounts/:id/unmute", MastodonAPIController, :relationship_noop)
Need to implement this support for MastodonAPI and TwitterAPI.
Related functionality (likely to be extracted to a separate issue depending on this one): import and export of mutes list for a user (FE request: pleroma-fe#220 (closed))