Resolve "Fix problematic Database/MultipleDatabases offenses"

What does this MR do and why?

We need to stop using ActiveRecord::Base. The connection/transaction from this class is not compatible with the multiple database project.

In this MR, I am fixing where we have the rubocop rule Database/MultipleDatabases ignored. I am removing the ActiveRecord::Base connection and using the proper one.

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Related to #335808 (closed)