Bug 35287: (Follow-up 37389): ExtendedAttributes

Bug 35287: (Follow-up 37389): ExtendedAttributes

Apply ExtendedAttributes Mixin to AdditionalFields

To test the ExtendedAttributes mixin search is working:
1) Create 2 or more searchable licenses additional fields
2) Create a new license and enter values in these searchable fields
3) Go to the licenses list, use the column filters to search on more
than one column, verify that the search work as intended (AND operator)

Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Paul Derscheid <paul.derscheid@lmscloud.de>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>