Add explicit attribute on enums on proj. c. violations

What does this MR do and why?

Add explicit attribute on enums on proj. c. violations

• Explicitly defining the attribute type for the enum columns to prevent schema loading errors Sidekiq contexts by providing type information before the database schema is fully initialized.

References

• https://new-sentry.gitlab.net/organizations/gitlab/issues/2524435/?alert_rule_id=12&alert_type=issue&notification_uuid=d75becdf-4339-4a04-b8fd-60cb9a054c6d&project=3&referrer=slack
• !207292 (merged)

How to set up and validate locally

0. Unsure how to.

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