Store URIs of follows, follow requests and blocks for ActivityPub (#7160)

Same URI passed between follow request and follow, since they are
the same thing in ActivityPub. Local URIs are generated during
creation using UUIDs and are passed to serializers.

app/lib/activitypub/activity/block.rb

@@ -7,6 +7,6 @@ class ActivityPub::Activity::Block < ActivityPub::Activity
     return if target_account.nil? || !target_account.local? || delete_arrived_first?(@json['id']) || @account.blocking?(target_account)
 
     UnfollowService.new.call(target_account, @account) if target_account.following?(@account)
-    @account.block!(target_account)
+    @account.block!(target_account, uri: @json['id'])
   end
 end

app/lib/activitypub/activity/follow.rb

@@ -12,7 +12,7 @@ class ActivityPub::Activity::Follow < ActivityPub::Activity
       return
     end
 
-    follow_request = FollowRequest.create!(account: @account, target_account: target_account)
+    follow_request = FollowRequest.create!(account: @account, target_account: target_account, uri: @json['id'])
 
     if target_account.locked?
       NotifyService.new.call(target_account, follow_request)

app/lib/activitypub/tag_manager.rb

@@ -38,6 +38,10 @@ class ActivityPub::TagManager
     end
   end
 
+  def generate_uri_for(_target)
+    URI.join(root_url, 'payloads', SecureRandom.uuid)
+  end
+
   def activity_uri_for(target)
     raise ArgumentError, 'target must be a local activity' unless %i(note comment activity).include?(target.object_type) && target.local?