ActivityPub: Add basic, read-only support for Outboxes, Notes, and Create/Announce Activities (#2197)

* Clean up collapsible components

* Expose user Outboxes and AS2 representations of statuses

* Save work thus far.

* Fix bad merge.

* Save my work

* Clean up pagination.

* First test working.

* Add tests.

* Add Forbidden error template.

* Revert yarn.lock changes.

* Fix code style deviations and use localized instead of hardcoded English text.

config/locales/en.yml

@@ -40,6 +40,15 @@ en:
     posts: Posts
     remote_follow: Remote follow
     unfollow: Unfollow
+  activitypub:
+    outbox:
+      name: "%{account_name}'s Outbox"
+      summary: "A collection of activities from user %{account_name}."
+    activity:
+      create:
+        name: "%{account_name} created a note."
+      announce:
+        name: "%{account_name} announced an activity."
   admin:
     accounts:
       are_you_sure: Are you sure?
@@ -206,6 +215,7 @@ en:
       x_months: "%{count}mo"
       x_seconds: "%{count}s"
   errors:
+    '403': You don't have permission to view this page.
     '404': The page you were looking for doesn't exist.
     '410': The page you were looking for doesn't exist anymore.
     '422':