Retention Policies for Immutability Tags

[Vad1mo]

Is your feature request related to a problem? Please describe.
Harbor only supports adding immutability rules. Once they are set, they need to be removed manually, one by one.
The only way to delete immutable objects is to turn off immutability,
run retention again, and turn it back on when you think you've deleted what you wanted.

Describe the solution you'd like
The Immutability Tag policy should be extended to not only "apply" immutability tags but also remove immutability tags.

Describe the main design/architecture of your solution
It would be false to delete images with Immutability Tags. To work around that problem, we need to introduce rules to immutability tags.

• Immutability rules will have one new action → RELEASE, next to the already existing and implicit action APPLY.
  • This can be done as a dropdown or a toggle
• An additional dropdown provides conditions under which the action is applied.
  • Possible options for condition action → APPLY
    • Immediately (this is like the current implicit behavior)
    • Pulled count greater → # count
    • tbd…
  • Possible options for condition action → RELEASE
    • Artifacts not pulled within the last # of days → # count days
    • Artifacts pushed # days ago → # count days
    • tbd…

Mockup of the new tag immutability rule, with actions and conditions.

Describe the development plan you've considered

• under investigation

Additional context
There are a few options under which conditions apply or release can happen, but I think there might be even more...