Bug: filter form should take care of restricted user rights

[nboisteault]

• Log as admin
• See only one point is visible
• But filter form display all possible values

[nboisteault]

@mdouchin to discuss

[Gustry]

Side note, but there is already filter_layer_by_user.qgs or similar project.
I think, I would appreciate if a project called filtered_layer_by_user has different aspects of this feature, like form filter.

Adding new layer doesn't matter, it takes times to update/upgrade a few projects for now).

[github-actions]

The Lizmap project highly values your contribution and would love to see this work merged! Unfortunately this PR has not had any activity in the last 2 months and is being automatically marked as "stale".
If there is no further activity on this pull request, it will be closed in two weeks.