Documentation - Support review of AutoDevops Topic Index

What does this MR do?

This is a first-step MR to address some of the items that came out of the docs review for the Auto DevOps Topic page.

This is only a first step to address a few items that came out of a technical accuracy review for some of the steps involved.

The section on the mismatch was removed because it dates back to the first introduction of the page and it seemed vague, it's not clear what errors might prompt a "mismatch" - and other instructions, including those in the Auto Test stage information, mention the need for "custom buildpacks" instead of .gitlab-ci.yml customizations.

The section on the :force_autodevops_on_by_default feature flag was removed, because it's been mentioned in one ticket that I could find, and then was about turning it off, not forcing it on. Researching it also turned out that there's a bug where it's not currently honored (either in GitLab.com or self-managed).

The Auto Devops Domain instructions were modified slightly because there's now Kubernetes clusters at the instance level. And the Auto Devops domain setting at the instance level is used as a fallback. (It also does not support all TLD's - see: #21748 (comment 352360399)

I am still trying to go through issues and tickets to see if there are Auto Devops patterns that could be served by mentions on this top level page - but I wanted to get something out there to keep moving forward here.

Related issues

gitlab-com/support/support-team-meta#2293 (closed)

Author's checklist (required)

• Follow the Documentation Guidelines and Style Guide.
• If you have developer access or higher (for example, GitLab team members or Core Team members)
  • Apply the documentation label, plus:
    • The corresponding DevOps stage and group label, if applicable.
    • development guidelines when changing docs under doc/development/*, CONTRIBUTING.md, or README.md.
    • development guidelines and Documentation guidelines when changing docs under development/documentation/*.
    • development guidelines and Description templates (.gitlab/*) when creating/updating issue and MR description templates.
  • Assign the designated Technical Writer.

When applicable:

• Update the permissions table.
• Link docs to and from the higher-level index page, plus other related docs where helpful.
• Add GitLab's version history note(s).
• Add the product tier badge.
• Add/update the feature flag section.
• If you're changing document headings, search doc/*, app/views/*, and ee/app/views/* for old headings replacing with the new ones to avoid broken anchors.

Review checklist

All reviewers can help ensure accuracy, clarity, completeness, and adherence to the Documentation Guidelines and Style Guide.

1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

• Optional: Technical writer review. If not requested for this MR, must be scheduled post-merge. To request for this MR, assign the writer listed for the applicable DevOps stage.
  • Add Technical Writing and docs:: workflow label.
  • Add docs-only when the only files changed are under doc/*.

3. Maintainer

1. Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
2. Ensure a release milestone is set.
3. If there has not been a technical writer review, create an issue for one using the Doc Review template.