Successful sync should cause verification

This is needed to support:

1. Verification of mutable types
2. Automatic healing of verification failures

Changelog: changed
EE: true

.gitlab/issue_templates/Geo Replicate a new Git repository type.md

@@ -513,6 +513,12 @@ That's all of the required database changes.
         last_synced_at { 1.day.ago }
         retry_count { 0 }
       end
+
+      trait :verification_succeeded do
+        verification_checksum { 'e079a831cab27bcda7d81cd9b48296d0c3dd92ef' }
+        verification_state { Geo::CoolWidgetRegistry.verification_state_value(:verification_succeeded) }
+        verified_at { 5.days.ago }
+      end
     end
   end
   ```

.gitlab/issue_templates/Geo Replicate a new blob type.md

@@ -479,6 +479,12 @@ That's all of the required database changes.
         last_synced_at { 1.day.ago }
         retry_count { 0 }
       end
+
+      trait :verification_succeeded do
+        verification_checksum { 'e079a831cab27bcda7d81cd9b48296d0c3dd92ef' }
+        verification_state { Geo::CoolWidgetRegistry.verification_state_value(:verification_succeeded) }
+        verified_at { 5.days.ago }
+      end
     end
   end
   ```

ee/app/models/concerns/geo/replicable_registry.rb

@@ -44,6 +44,11 @@ module Geo::ReplicableRegistry
     end
   end
 
+  # Overridden by Geo::VerifiableRegistry
+  def after_synced
+    # No-op
+  end
+
   def replicator_class
     Gitlab::Geo::Replicator.for_class_name(self)
   end
@@ -86,6 +91,10 @@ module Geo::ReplicableRegistry
         registry.retry_at = nil
       end
 
+      after_transition any => :synced do |registry, _|
+        registry.after_synced
+      end
+
       event :start do
         transition [:pending, :synced, :failed] => :started
       end

ee/app/models/concerns/geo/verifiable_registry.rb

@@ -3,6 +3,7 @@
 module Geo
   module VerifiableRegistry
     extend ActiveSupport::Concern
+    extend ::Gitlab::Utils::Override
     include ::Gitlab::Geo::VerificationState
 
     class_methods do
@@ -79,5 +80,10 @@ module Geo
         verification_succeeded_with_checksum!(checksum, calculation_started_at)
       end
     end
+
+    override :after_synced
+    def after_synced
+      self.verification_pending!
+    end
   end
 end

ee/lib/gitlab/geo/verification_state.rb

@@ -270,7 +270,7 @@ module Gitlab
         end
       end
 
-      # Overridden by ReplicableRegistry
+      # Overridden by Geo::VerifiableRegistry
       def clear_verification_failure_fields!
         self.verification_retry_count = 0
         self.verification_retry_at = nil

ee/spec/factories/geo/package_file_registry.rb

@@ -22,5 +22,11 @@ FactoryBot.define do
       last_synced_at { 1.day.ago }
       retry_count { 0 }
     end
+
+    trait :verification_succeeded do
+      verification_checksum { 'e079a831cab27bcda7d81cd9b48296d0c3dd92ef' }
+      verification_state { Geo::PackageFileRegistry.verification_state_value(:verification_succeeded) }
+      verified_at { 5.days.ago }
+    end
   end
 end

ee/spec/factories/geo/pipeline_artifact_registry.rb

@@ -22,5 +22,11 @@ FactoryBot.define do
       last_synced_at { 1.day.ago }
       retry_count { 0 }
     end
+
+    trait :verification_succeeded do
+      verification_checksum { 'e079a831cab27bcda7d81cd9b48296d0c3dd92ef' }
+      verification_state { Geo::PipelineArtifactRegistry.verification_state_value(:verification_succeeded) }
+      verified_at { 5.days.ago }
+    end
   end
 end

ee/spec/factories/geo/snippet_repository_registry.rb

@@ -22,5 +22,11 @@ FactoryBot.define do
       last_synced_at { 1.day.ago }
       retry_count { 0 }
     end
+
+    trait :verification_succeeded do
+      verification_checksum { 'e079a831cab27bcda7d81cd9b48296d0c3dd92ef' }
+      verification_state { Geo::SnippetRepositoryRegistry.verification_state_value(:verification_succeeded) }
+      verified_at { 5.days.ago }
+    end
   end
 end

ee/spec/factories/geo/terraform_state_version_registry.rb

@@ -22,5 +22,11 @@ FactoryBot.define do
       last_synced_at { 1.day.ago }
       retry_count { 0 }
     end
+
+    trait :verification_succeeded do
+      verification_checksum { 'e079a831cab27bcda7d81cd9b48296d0c3dd92ef' }
+      verification_state { Geo::TerraformStateVersionRegistry.verification_state_value(:verification_succeeded) }
+      verified_at { 5.days.ago }
+    end
   end
 end

ee/spec/support/shared_examples/models/geo_verifiable_registry_shared_examples.rb

@@ -7,6 +7,18 @@ RSpec.shared_examples 'a Geo verifiable registry' do
 
   subject(:registry_record) { create(registry_class_factory, :synced) }
 
+  context 'state machine' do
+    context 'when transitioning to synced' do
+      it 'marks verification as pending' do
+        registry = create(registry_class_factory, :started, :verification_succeeded)
+
+        registry.synced!
+
+        expect(registry.reload).to be_verification_pending
+      end
+    end
+  end
+
   describe '.verification_pending_batch' do
     before do
       subject.save!