Subtransactions: RubyGems metadata extraction detected 2022-04-05 in sidekiq job

Runbook: https://gitlab.com/gitlab-com/runbooks/-/blob/master/docs/patroni/postgresql-subtransactions.md

Backtrace:

lib/gitlab/database/transaction/observer.rb:42:in `block in register!'
app/models/application_record.rb:86:in `block in safe_find_or_create_by'
app/models/concerns/cross_database_modification.rb:93:in `block in transaction'
lib/gitlab/database.rb:320:in `block in transaction'
lib/gitlab/database.rb:319:in `transaction'
app/models/concerns/cross_database_modification.rb:84:in `transaction'
app/models/application_record.rb:86:in `safe_find_or_create_by'
app/models/application_record.rb:56:in `safe_find_or_create_by!'
app/services/packages/rubygems/metadata_extraction_service.rb:52:in `metadatum'
app/services/packages/rubygems/metadata_extraction_service.rb:23:in `write_metadata'
app/services/packages/rubygems/metadata_extraction_service.rb:12:in `execute'
app/services/packages/rubygems/process_gem_service.rb:34:in `block (2 levels) in process_gem'
app/models/concerns/cross_database_modification.rb:93:in `block in transaction'
lib/gitlab/database.rb:320:in `block in transaction'
lib/gitlab/database.rb:319:in `transaction'
app/models/concerns/cross_database_modification.rb:84:in `transaction'
app/services/packages/rubygems/process_gem_service.rb:31:in `block in process_gem'
app/services/concerns/exclusive_lease_guard.rb:29:in `try_obtain_lease'
app/services/packages/rubygems/process_gem_service.rb:30:in `process_gem'
app/services/packages/rubygems/process_gem_service.rb:20:in `execute'
app/workers/packages/rubygems/extraction_worker.rb:21:in `perform'
lib/gitlab/application_context.rb:93:in `block in use'
lib/gitlab/application_context.rb:93:in `use'
lib/gitlab/application_context.rb:44:in `with_context'
lib/gitlab/sidekiq_versioning/middleware.rb:9:in `call'
lib/gitlab/database/query_analyzer.rb:46:in `within'
lib/gitlab/with_request_store.rb:17:in `enabling_request_store'
lib/gitlab/with_request_store.rb:10:in `with_request_store'
lib/gitlab/sidekiq_daemon/monitor.rb:49:in `within_job'

Elastic Log entry: https://log.gprd.gitlab.net/goto/f27e1890-b51a-11ec-b73f-692cc1ae8214

cc/ @stanhu @grzesiek