WIP: Track Historical Information for the gitlab_subscriptions table

What does this MR do?

We plan to track changes to the gitlab_subscriptions using Snowplow events as discussed in this issue open by the data team #13297 (moved)

The gitlab_subscription records the current state of our gitlab_subscriptions. The records are slowly mutable. On the contrary, Snowplow will receive and store sequences of immutable events. Upon any creation, update or deletion event (does that happen ?) in our database a new row will be added with all metadata attached to the specific object. This table will allow us to keep track of all changes happening in the database. For example status changes of a specific subscription (from active to expire, or from trial started to active subscriptions...)

Screenshots

N/A

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Reviews

• Database Review https://docs.gitlab.com/ee/development/database_review.html
• Backend Review https://docs.gitlab.com/ee/development/database_review.html
• Data Analyst Review https://docs.gitlab.com/ee/development/database_review.html

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #13297 (moved)