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

spec/services/fetch_link_card_service_spec.rb

@@ -55,7 +55,7 @@ RSpec.describe FetchLinkCardService do
   end
 
   context 'in a remote status' do
-    let(:status) { Fabricate(:status, uri: 'abc', text: 'Habt ihr ein paar gute Links zu #<span class="tag"><a href="https://quitter.se/tag/wannacry" target="_blank" rel="tag noopener" title="https://quitter.se/tag/wannacry">Wannacry</a></span> herumfliegen?   Ich will mal unter <br> <a href="https://github.com/qbi/WannaCry" target="_blank" rel="noopener" title="https://github.com/qbi/WannaCry">https://github.com/qbi/WannaCry</a> was sammeln. !<a href="http://sn.jonkman.ca/group/416/id" target="_blank" rel="noopener" title="http://sn.jonkman.ca/group/416/id">security</a>&nbsp;') }
+    let(:status) { Fabricate(:status, account: Fabricate(:account, domain: 'example.com'), text: 'Habt ihr ein paar gute Links zu #<span class="tag"><a href="https://quitter.se/tag/wannacry" target="_blank" rel="tag noopener" title="https://quitter.se/tag/wannacry">Wannacry</a></span> herumfliegen?   Ich will mal unter <br> <a href="https://github.com/qbi/WannaCry" target="_blank" rel="noopener" title="https://github.com/qbi/WannaCry">https://github.com/qbi/WannaCry</a> was sammeln. !<a href="http://sn.jonkman.ca/group/416/id" target="_blank" rel="noopener" title="http://sn.jonkman.ca/group/416/id">security</a>&nbsp;') }
 
     it 'parses out URLs' do
       expect(a_request(:head, 'https://github.com/qbi/WannaCry')).to have_been_made.at_least_once