Activity log retention time

[nelsonkopliku]

Description

Adds the foundation for the activity log settings, specifically retention time.

• migration to add the required fields into the settings STI
• schema and constraints
• initial default retention time is provided
• context exposing basic read/update operations

The context functions can be then used in a controller to expose desired operations.

[gagandeepb]

Adding some comments for later consideration.

[nelsonkopliku]

hey @gagandeepb, @balanza, I think I have addressed what we discussed:

• removed the save retention time operation as we do not really have to cover that use case
• init default retention time to 1 month at application startup, and in seeds for dev environment
• now the settings table has only one field retention_time, being an embedded value object stored as json *
• renamed the whole thing to Activity Log, as per naming discussions 🙈

* Note that this moves possible validation errors one level down in Trento.ActivityLog.Settings (we get changeset errors on the embedded RetentionTime), and I am not sure our error handling at controller level is ready for this.
It might end up in not being an issue, but we'll discover more when actually implementing the controller.
If anything needs to be changed, we'll do so.

Thanks for the feedbacks!

[nelsonkopliku]

I realized that while rolling back, only the activity_log_retention_time field was removed, but the record typed activity_log_settings remained, meaning that migrating forward again would result in having the activity log settings record with a null retention time.

In order to avoid unwanted side effects I thought it is reasonable just deleting the whole record.

[balanza]

LGTM, I just have some thoughts on naming but they're non blocking