Add the ways needed to authenticate to the registry via CI/CD
What does this MR do?
Enhances documentation based on user feedback gitlab-com/support-forum#3825 (comment 96686175).
- Apply the correct labels and milestone
- Crosslink the document from the higher-level index
- Crosslink the document from other subject-related docs
- Correctly apply the product badges and tiers
Port the MR to EE (or backport from CE): always recommended, required when the
- Your team's review (required)
- PM's review (recommended, but not a blocker)
- Technical writer's review (required)
- Merge the EE-MR first, CE-MR afterwards