Description of problem:
Incremental Content View feature serves as a "hotfix process" to update a content in a given CV/LE without the need to publishing a new CV version, overwriting its Library environment and re-promoting it to the given LE.

However, this is supported for adding a content only, not for removing.

There are use cases where a package is required to be removed from a given CV/LE. The only allowed / supported way is to remove the package from the root repo, publish a new version of the CV and promote it to the LE. That does not work well when other changes happened to the repo or CV meantime. Therefore we need "decremental CV update" as well.

Version-Release number of selected component (if applicable):
Sat 6.10

How reproducible:
100%

Steps to Reproduce:
1. Attempt to remove a package from a CV/LE (while a newer CV version exists and the underlying repo got some more content)

Actual results:
1. No way of getting that. Even trying to use direct API requests fails when calling endpoint:

PUT /katello/api/repositories/:id/remove_packages

due to:

"Can only remove content from within the Default Content View"

Expected results:
Some allowed+supported way of removing a content from a CV/LE.

Additional info: