Add Reports to Admin API

CHANGELOG.md

docs/api/admin_api.md

lib/pleroma/activity.ex

lib/pleroma/emails/admin_email.ex

lib/pleroma/web/activity_pub/activity_pub.ex

lib/pleroma/web/activity_pub/utils.ex

lib/pleroma/web/admin_api/admin_api_controller.ex

lib/pleroma/web/admin_api/views/report_view.ex

lib/pleroma/web/common_api/common_api.ex

lib/pleroma/web/common_api/utils.ex

lib/pleroma/web/router.ex

...igrations/20190511191044_set_default_state_to_reports.exs

test/support/factory.ex

test/web/admin_api/admin_api_controller_test.exs

test/web/common_api/common_api_test.exs

test/web/mastodon_api/mastodon_api_controller_test.exs