New REST endpoint GET allowlist of CI_JOB_TOKEN access settings

What does this MR do and why?

• This MR works towards the another task of the issue (feature) #351740 (closed)

🛠 with ❤ at Siemens

Screenshots or screen recordings

• New REST endpoint for allowlist of CI_JOB_TOKEN access settings
  • GET "api/v4/projects/:id/job_token_scope/allowlist/inbound"
• The response is paginated
• The response contains a list of projects (basic project object)

How to set up and validate locally

1. Create a personal access token with the respective permissions
2. Ensure the user of the personal access token is at least maintainer of the project
3. Execute the following curl commands

curl --request GET \
  --url http://127.0.0.1:3000/api/v4/projects/7/job_token_scope/allowlist/inbound?private_token=<personal_access_token_of_project_maintainer>

TODO

• @gerardo-navarro Add pagination
• @gerardo-navarro Add guard for respective flag ci_inbound_token_scope_enabled
• Check with gitlab team regarding order of allowlist allow list
• Check with gitlab team regarding the data fields in response object
• @gerardo-navarro Add test to check that only the direction are not possible
• Approval from technical writer
• @gerardo-navarro Remove api endpoint for outbound <= see !118495 (comment 1376769595)

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

• Changelog entry added, if necessary

• Documentation created/updated via this MR

• Documentation reviewed by technical writer or follow-up review issue created

• Tests added for this feature/bug

• Tested in all supported browsers

• Conforms to the code review guidelines

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• Conforms to the style guides

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• Wait for the following MR to be merged to master: New REST api endpoint to fetch CI_JOB_TOKEN acc... (!117842 - merged)

• Wait for the following MR to be merged to master: New REST endpoint PATCH CI_JOB_TOKEN access set... (!118357 - merged)

Related to #351740 (closed)