Persist mutations locally only when the request complete successfully

I removed it because actually, the patch already happens in the `onMutate` callback. However, it makes me wonder if we shouldn't move this to the `onSuccess` so that patch events are locally persisted only if the request is completed successfully.

_Originally posted by @swouf in https://github.com/graasp/graasp-apps-query-client/pull/142#discussion_r1286002277_

Start by locating the mutation implementation that uses the onMutate and onSuccess callbacks, then read how patch events are persisted and how request failures are handled. Done means persistence happens only after a successful request, with the relevant success and failure behavior covered by tests.

Written by the indexing model from the issue text.