[Task]: Apply add-on name validation to users & collection names

[diox]

Description

https://bugzilla.mozilla.org/show_bug.cgi?id=1991400 was recently fixed and tightened validation of add-on names. The same should be applied to user and collection names - essentially renaming validate_addon_name to validate_name and using that function for collections and users as well.

The existing validation for users & collections names should stay - this would be added on top. See also https://bugzilla.mozilla.org/show_bug.cgi?id=1980900

Acceptance Criteria

• Add-on name validation is also applied to collections & users

┆Issue is synchronized with this Jira Task