[#468] Merged `upstream/develop`.

docs/Admin-API.md

lib/pleroma/user.ex

lib/pleroma/user/info.ex

lib/pleroma/web/activity_pub/activity_pub.ex

lib/pleroma/web/admin_api/admin_api_controller.ex

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

lib/pleroma/web/mastodon_api/views/account_view.ex

lib/pleroma/web/router.ex

test/user_test.exs

test/web/activity_pub/activity_pub_test.exs

test/web/admin_api/admin_api_controller_test.exs

test/web/mastodon_api/mastodon_api_controller_test.exs