Add Resource Root URL test for permissions assigned to groups

[daniel-beck]

Vaguely motivated by JENKINS-73720: Confirm Resource Root URL works in principle when permissions are assigned to groups.

Testing done

n/a

Proposed changelog entries

n/a

Proposed upgrade guidelines

N/A

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1. The Jira issue, if it exists, is well-described.
2. The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
3. There is automated testing or an explanation as to why this change has no tests.
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7. For dependency updates, there are links to external changelogs and, if possible, full differentials.
8. For new APIs and extension points, there is a link to at least one consumer.

Desired reviewers

@mention

Before the changes are marked as ready-for-merge:

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[daniel-beck]

Commenting out this line makes the test fail.