Edit Collection: default item/bitstream read rights: It should be possible to link to a different group without deleting the current linked one

[bram-atmire]

Describe the bug

When a specific group is linked to collection default item and/or bitstream read operations, the only possibility to modify this relation is to delete the linked group.

This is particularly problematic for institutions upgrading to DSpace 7 and newer, who have linked the same group to different collection default item/bitstream read settings, who only want to make a change for particular collections.

In DSpace 7, if NO default item/bitstream read rights are set on collection level, the button "Restrict" forces the creation of a new group, dedicated to this single purpose. BUT: I assume this was not always the case in older versions of DSpace, where a selector interface was offered to select an existing group.

To Reproduce

Steps to reproduce the behavior:

1. Go to edit collection - assign roles, for a collection that already has item or bitstream read DEFAULT restrictions
2. Try to apply the restriction to a different group, without deleting the current one

Expected behavior

It should be possible to link to another group without deleting the current one.

[tdonohue]

I'm not sure how easy this will be. It looks like the default COLLECTION_[UUID]_[TYPE]_DEFAULT_READ group for Items and Bitstreams is hardcoded in several areas of the codebase. See all usages of CollectionServiceImpl.getDefaultReadGroupName()

Also, fair warning, this code to hardcode the group name was added in 7.1 to fix a security issue: GHSA-cf2j-vf36-c6w8 So, we'd need to be very careful with removing it or updating it.

Flagging this as "needs discussion" as I think this requires more investigation.