Hard exception when database connection opened in routes

Thong Kuahrequested to merge
raise_on_new_connection_in_routes into master

What does this MR do and why?

Now that we have addressed all warnings, turn it to a hard exception

This helps prevents database connections not dropped because connections are held open

See also https://github.com/rails/rails/issues/44875

Related issue: #359913 (closed)

Screenshots or screen recordings

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How to set up and validate locally

  1. Add something like Project.first within config/routes.rb
  2. You should see the following error when running bundle exec rails console:
	24: from (eval):3:in `draw_route'
	23: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/querying.rb:22:in `first'
	22: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/relation/finder_methods.rb:122:in `first'
	21: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/relation/finder_methods.rb:538:in `find_nth'
	20: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/relation/finder_methods.rb:545:in `find_nth_with_limit'
	19: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/relation/finder_methods.rb:579:in `ordered_relation'
	18: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/relation/delegation.rb:93:in `primary_key'
	17: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/attribute_methods/primary_key.rb:71:in `primary_key'
	16: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/attribute_methods/primary_key.rb:83:in `reset_primary_key'
	15: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/attribute_methods/primary_key.rb:95:in `get_primary_key'
	14: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/model_schema.rb:380:in `table_exists?'
	13: from /Users/tkuah/code/gdk-ee/gitlab/lib/gitlab/database/load_balancing/connection_proxy.rb:89:in `method_missing'
	12: from /Users/tkuah/code/gdk-ee/gitlab/lib/gitlab/database/load_balancing/connection_proxy.rb:119:in `write_using_load_balancer'
	11: from /Users/tkuah/code/gdk-ee/gitlab/lib/gitlab/database/load_balancing/load_balancer.rb:111:in `read_write'
	10: from /Users/tkuah/code/gdk-ee/gitlab/lib/gitlab/database/load_balancing/load_balancer.rb:184:in `retry_with_backoff'
	 9: from /Users/tkuah/code/gdk-ee/gitlab/lib/gitlab/database/load_balancing/load_balancer.rb:112:in `block in read_write'
	 8: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/abstract/connection_pool.rb:428:in `connection'
	 7: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/abstract/connection_pool.rb:588:in `checkout'
	 6: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/abstract/connection_pool.rb:866:in `acquire_connection'
	 5: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/abstract/connection_pool.rb:905:in `try_to_checkout_new_connection'
	 4: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/abstract/connection_pool.rb:926:in `checkout_new_connection'
	 3: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/abstract/connection_pool.rb:882:in `new_connection'
	 2: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/abstract/connection_pool.rb:882:in `public_send'
	 1: from /Users/tkuah/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/postgresql_adapter.rb:37:in `postgresql_connection'
/Users/tkuah/code/gdk-ee/gitlab/config/initializers/00_connection_logger.rb:15:in `new_client': Database connection should not be called during initializers. Read more at https://docs.gitlab.com/ee/development/rails_initializers.html#database-connections-in-initializers (RuntimeError)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

Edited by Thong Kuah

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