Resolve various database deprecation warnings (!23772) · Merge requests · GitLab.org / GitLab FOSS · GitLab

What does this MR do?

This resolves various deprecations triggered by extending ActiveRecord::Migration, and by using table_exists? instead of data_source_exists?.

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/54478, though this issue may need further work to replace all instances of table_exists? that might be deprecated.

Does this MR meet the acceptance criteria?

Documentation created/updated
Conforms to the code review guidelines
Conforms to the merge request performance guidelines
Conforms to the style guides
Conforms to the database guides
Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
Security reports checked/validated by reviewer