[GitLab] Group membership check fails for subgroups

[zragge]

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Bug description

When using subgroup-membership for authorization the gitlab authenticator always says that the user is not a member of the groups. It seems to me that this is because the _check_membership_allowed_groups does url-encoding twice. First on row 206 in the mapping function (url_escape) and then on row 209 in the quote function. This causes the / in between the main and the subgroup to first becoming %2F, and then %252F when encoded the second time. When this then is sent to the gitlab-api it does not recognise the group.

I tried to remove one of the encoding functions in _check_membership_allowed_groups, and that seems to work for me.

Expected behaviour

Authorization succeeds

Actual behaviour

Authorization fails

How to reproduce

Create a subgroup in gitlab and use gitlab oauthenticator

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