allow the support bot to be considered "subscribed"

unless explicitly unsubscribed

app/models/ee/issue.rb

@@ -6,5 +6,30 @@ module EE
 
       super
     end
+
+    # override
+    def subscribed_without_subscriptions?(user, *)
+      # TODO: this really shouldn't be necessary, because
+      # the support bot should be a participant (which is
+      # what the superclass method checks for). However,
+      # the support bot is not permitted to :read_project
+      # the project, so it gets filtered out at the end of
+      # Participable#raw_participants. Overriding *that*
+      # behavior is problematic because it doesn't use the
+      # Policy framework, and instead uses a custom-coded
+      # Ability.users_that_can_read_project, which is...
+      # a pain to override in EE. So... here we say, the
+      # support bot is subscribed by default, until an
+      # unsubscribed record appears, even though it's not
+      # *technically* a participant in this issue.
+      #
+      # Making the support bot subscribed to every issue
+      # is not as bad as it seems, though, since it isn't
+      # permitted to :receive_notifications, and doesn't
+      # actually show up in the participants list.
+      return true if user == ::User.support_bot
+
+      super
+    end
   end
 end