AP refactoring.

lib/pleroma/object.ex

lib/pleroma/plugs/authentication_plug.ex

lib/pleroma/user.ex

lib/pleroma/web/activity_pub/activity_pub.ex

lib/pleroma/web/activity_pub/utils.ex

lib/pleroma/web/ostatus/ostatus.ex

lib/pleroma/web/twitter_api/twitter_api.ex

test/plugs/authentication_plug_test.exs

test/support/builders/activity_builder.ex

test/support/factory.ex

test/web/activity_pub/activity_pub_test.exs

test/web/salmon/salmon_test.exs