fix: Disable enqueueing Avatar jobs if the URL is invalid (#12035)

- Add a new queue purgable
- Disable enqueuing the job if URL is invalid

spec/jobs/avatar/avatar_from_gravatar_job_spec.rb

@@ -7,7 +7,7 @@ RSpec.describe Avatar::AvatarFromGravatarJob do
 
   it 'enqueues the job' do
     expect { described_class.perform_later(avatarable, email) }.to have_enqueued_job(described_class)
-      .on_queue('low')
+      .on_queue('purgable')
   end
 
   it 'will call AvatarFromUrlJob with gravatar url' do

spec/jobs/avatar/avatar_from_url_job_spec.rb

@@ -6,7 +6,7 @@ RSpec.describe Avatar::AvatarFromUrlJob do
 
   it 'enqueues the job' do
     expect { described_class.perform_later(avatarable, avatar_url) }.to have_enqueued_job(described_class)
-      .on_queue('low')
+      .on_queue('purgable')
   end
 
   it 'will attach avatar from url' do