Switch to static URIs, new URI format in both protocols for new statuses (#4815)

* Decouple Status#local? from uri being nil

* Replace on-the-fly URI generation with stored URIs

- Generate URI in after_save hook for local statuses
- Use static value in TagManager when available, fallback to tag format
- Make TagManager use ActivityPub::TagManager to understand new format
- Adjust tests

* Use other heuristic for locality of old statuses, do not perform long query

* Exclude tombstone stream entries from Atom feed

* Prevent nil statuses from landing in Pubsubhubbub::DistributionWorker

* Fix URI not being saved (#4818)

* Add more specs for Status

* Save generated uri immediately

and also fix method order to minimize diff.

* Fix alternate HTML URL in Atom

* Fix tests

* Remove not-null constraint from statuses migration to speed it up

app/controllers/accounts_controller.rb

@@ -22,7 +22,7 @@ class AccountsController < ApplicationController
 
       format.atom do
         @entries = @account.stream_entries.where(hidden: false).with_includes.paginate_by_max_id(20, params[:max_id], params[:since_id])
-        render xml: OStatus::AtomSerializer.render(OStatus::AtomSerializer.new.feed(@account, @entries.to_a))
+        render xml: OStatus::AtomSerializer.render(OStatus::AtomSerializer.new.feed(@account, @entries.reject { |entry| entry.status.nil? }))
       end
 
       format.json do