[Request] Add capability to report a problem with a given document or layer

[mradamcox]

Describe the feature or enhancement you're looking for
This could be as simple as a flag for review action, but the ability to actually leave comments on resource, which did exist in the original GeoNode design, would be a great thing to add back into the system.

If this request is linked to a problem, please describe.
No comprehensive way to review content across multiple volumes, or the system as a whole.