add "owner" as valid access level for the group_access_token resource

[defreng]

Description

The Gitlab API documentation does not mention the possibility to select access level 50 (=owner), but this option is both working (I verified it manually with an API call) and also exposed in the Gitlab UI:

PR Checklist Acknowledgement

• I acknowledge that all of the following items are true, where applicable:
  • Resource attributes match 1:1 the names and structure of the API resource in the GitLab API documentation.
  • Examples are updated with:
    • A *.tf file for the resource/s with at least one usage example
    • A *.sh file for the resource/s with an import example (if applicable)
  • New resources have at minimum a basic test with three steps:
    • Create the resource
    • Update the attributes
    • Import the resource
  • No new //lintignore comments were copied from existing code. (Linter rules are meant to be enforced on new code.)

[github-actions]

Welcome @defreng 👋

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Thanks again, and welcome to the community! 😃

[timofurrer]

Aleeexx 👋

Can you prove that it works by adding a new test step? 💃

[defreng]

Timo! 🙌

Would you have any objections against just changing the existing tests to use the "owner" access level instead of maintainer?

[timofurrer]

Hmmm, I think eventually it would be nice to check all the accepted access levels (maybe something for another PR though). Thus, let's add a separate test step :)

[timofurrer]

@defreng Can you please rebase so that the tests are passing again?

[defreng]

done 🙂

[armsnyder]

lgtm 🚀

[timofurrer]

LGTM 🎉