Currently a work package can only be shared with users.

Now a work package should be shared with a group as well (see #31150 for the specification of how this is supposed to look like in the modal).

This requires at least:

* [x] Adding groups to the autocompleter
* [x] Adding groups to the list of shared with users
* [x] Note that the members are not listed individually unless they are shared with individually as well.
* [x] Fanning out the groups work package member to all users being part of the group
* [ ] Sending mails for every user part of the group
* [x] Removing the work package members if a users is removed from a group or if the group is deleted
* [x] Allowing to override the role granted to the group for an individual user and correctly displaying the role for that
* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion Dealing with a user being part of two groups for which different roles have been assigned.
* [x] I'm pretty sure the above refers to actually permission checking. If so, it's most likely covered in the work Klaus is doing for permission checking. If so, and this bullet point only covers role rendering, we're good 😁