Add "links" collection to index resources, again

[pfeuffer]

Proposed changes

With the introduction of react-query, it looks like the indexResources attribute of the repository initialization extension properties lost its collection links, which was replaces by _links. In this fix we copy this collection, so that the template plugin still can use links.

Fixes #1593

Your checklist for this pull request

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• PR is well described and the description can be used as commit message on squash
• Related issues linked to PR if existing and labels set
• Target branch is not master (in most cases develop should bet the target of choice)
• Code does not conflict with target branch
• Changelog entry file created in gradle/changelog
• Definition of Done's fulfilled: DoD // UI DoD

Checklist for branch merge request (not required for forks)

• Branch is green/blue on Jenkins
• Quality Gate passed on SonarQube

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

0.0% Coverage
0.0% Duplication