Merge branch 'security/actor-containment' into 'develop'

lib/pleroma/web/activity_pub/activity_pub.ex

...tures/httpoison_mock/https___info.pleroma.site_actor.json

...res/httpoison_mock/https__info.pleroma.site_activity.json

...es/httpoison_mock/https__info.pleroma.site_activity2.json

...es/httpoison_mock/https__info.pleroma.site_activity3.json

test/support/httpoison_mock.ex

test/web/activity_pub/transmogrifier_test.exs