Fix subscriptions:clear task, refactor feeds, refactor streamable activites

and atom feed generation to some extent, as well as the way mentions are
stored

spec/models/account_spec.rb

@@ -96,18 +96,6 @@ RSpec.describe Account, type: :model do
     end
   end
 
-  describe '#title' do
-    it 'is the same as the username' do
-      expect(subject.title).to eql subject.username
-    end
-  end
-
-  describe '#content' do
-    it 'is the same as the note' do
-      expect(subject.content).to eql subject.note
-    end
-  end
-
   describe '#ping!' do
     pending
   end

spec/models/favourite_spec.rb

@@ -42,12 +42,6 @@ RSpec.describe Favourite, type: :model do
     end
   end
 
-  describe '#mentions' do
-    it 'is always empty' do
-      expect(subject.mentions).to be_empty
-    end
-  end
-
   describe '#thread' do
     it 'equals the target' do
       expect(subject.thread).to eq subject.target

spec/models/follow_spec.rb

@@ -35,10 +35,4 @@ RSpec.describe Follow, type: :model do
       expect(subject.target).to eq bob
     end
   end
-
-  describe '#mentions' do
-    it 'is empty' do
-      expect(subject.mentions).to be_empty
-    end
-  end
 end

spec/models/status_spec.rb

@@ -40,31 +40,6 @@ RSpec.describe Status, type: :model do
     end
   end
 
-  describe '#mentions' do
-    before do
-      bob # make sure the account exists
-    end
-
-    it 'is empty if the status is self-contained and does not mention anyone' do
-      expect(subject.mentions).to be_empty
-    end
-
-    it 'returns mentioned accounts' do
-      subject.mentioned_accounts.create!(account: bob)
-      expect(subject.mentions).to include bob
-    end
-
-    it 'returns account of the replied-to status' do
-      subject.thread = other
-      expect(subject.mentions).to include bob
-    end
-
-    it 'returns the account of the shared status' do
-      subject.reblog = other
-      expect(subject.mentions).to include bob
-    end
-  end
-
   describe '#verb' do
     it 'is always post' do
       expect(subject.verb).to be :post