use flags in regex for "Group whitelist regex"

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Feature request

Which Nextcloud Version are you currently using: (see administration page)
31.0.3

Is your feature request related to a problem? Please describe.
Yes, I have multiple groups for my users in a Authentik backend, I want those groups to be automatically provisioned and added to the respective user. Currently this only works with exactly ONE group.
For example I have a user who has three groups in Authentik, let's say they are called "admin", "extern", "temporary", if I use this regular expression (admin|extern|temporary) the user_oidc plugin only matches the first thing it can find, since apparently the regular expression in this plugin doesn't use the /g flag.

Describe the solution you'd like
I'd like to see an option to set flags like /g to make sure multiple matches are possible.

Describe alternatives you've considered
I tired multiple variants of regex and none of them accepts more than the first match. I didn't find any other alternative.

Start by tracing how the user_oidc plugin handles the “Group whitelist regex” setting and applies it to Authentik groups. Confirm how regex flags are currently represented, then verify that a user with multiple matching groups has all of them provisioned rather than only the first match.