doc: Clarify release asset link schemes

What does this MR do and why?

doc: Clarify release asset link schemes

The current documentation claims, that "any URL" is supported, which is wrong: There are many schemes but GitLab only allows http, https and ftp. Using anything else like docker or file results in an API error:

release failed after 0.97 seconds. error=POST https://…/api/v4/projects/…/releases/…/assets/links: 400 {message: [Url is blocked: Only allowed schemes are http, https, ftp]}

The web-based GUI3,4 and the backend already validate the scheme, but using the CLI is it easy to run into that error as the constraint is not documented.

Change the wording to make it clear, that only those 3 schemes are allowed.

Signed-off-by: Philipp Hahn p.hahn@avm.de

References

• https://docs.gitlab.com/ci/yaml/#releaseassetslinks

How to set up and validate locally

1. setup a project and use release-cli or glab release to create a release

stages: [release]
create-release:
  stage: release
  rules:
    - if: "$CI_COMMIT_TAG"
  image: "registry.gitlab.com/gitlab-org/release-cli:latest"
  script: 'echo "Creating release $CI_COMMIT_TAG"'
  release:
    name: 'Release $CI_COMMIT_TAG'
    # description: release_notes.md
    tag_name: "$CI_COMMIT_TAG"
    ref: '$CI_COMMIT_SHA'
    assets:
      links:
        - name: 'Docker image for $CI_COMMIT_TAG'
          url: "$CI_REGISTRY_IMAGE/gu:$CI_COMMIT_TAG"
          link_type: "image"

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