Merge branch 'get_by_id' into 'develop'

Replace `Repo.get(Module, id)` with `Module.get_by_id(id)` where possible

See merge request pleroma/pleroma!1009

diff --cc test/user_test.exs
Simple merge

diff --cc test/web/mastodon_api/mastodon_api_controller_test.exs
Simple merge