Add ActivityPub actor representing the entire server (#11321)

* Add support for an instance actor

* Skip username validation for local Application accounts

* Add migration script to create instance actor

* Make Codeclimate happy

* Switch to id -99 for instance actor

* Remove unused `icon` and `image` attributes from instance actor

* Use if/elsif/else instead of return + ternary operator

* Add instance actor to fresh installs

* Use instance actor as instance representative

Use instance actor for forwarding reports, relay operations, and spam
auto-reporting.

* Seed database in test environment

* Fix single-user mode

* Fix tests

* Fix specs to accomodate for an extra `Account`

* Auto-reject follows on instance actor

Following an instance actor might make sense, but we are not handling that
right now, so auto-reject.

* Fix webfinger lookup and serialization for instance actor

* Rename instance actor

* Make it clear in the HTML view that the instance actor should not be blocked

* Raise cache time for instance actor as there's no dynamic content

* Re-use /about/more with a flash message for instance actor profile

1 files changed, 2 insertions, 0 deletions

diff --git a/app/views/about/more.html.haml b/app/views/about/more.html.haml
index b248ed1d2..21431ef8e 100644
--- a/app/views/about/more.html.haml
+++ b/app/views/about/more.html.haml
@@ -43,5 +43,7 @@
           = mail_to @instance_presenter.site_contact_email, nil, title: @instance_presenter.site_contact_email
 
   .column-3
+    = render 'application/flashes'
+
     .box-widget
       .rich-formatting= @instance_presenter.site_extended_description.html_safe.presence || t('about.extended_description_html')