[FF] `ci_interpolation_split_function` rollout issue

## Summary This issue is to roll out the split() interpolation function on production, that is currently behind the `ci_interpolation_split_function` feature flag. Introduced in: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/242134 ## Owners - Most appropriate Slack channel to reach out to: `#g_pipeline-authoring` - Best individual to reach out to: @lauraXD ## Expectations ### What are we expecting to happen? The split() function will become available in CI/CD interpolation blocks, allowing users to split comma-separated (or other delimiter-separated) string inputs into arrays for use in keys that accept arrays (like tags:). ### What can go wrong and how would we detect it? - Config validation could fail if split() is used in non-terminal position (chained with other functions) - Performance impact if widely adopted in large configs - Monitor error rates in CI config validation ## Rollout Steps Note: Please make sure to run the chatops commands in the Slack channel that gets impacted by the command. ### Rollout on non-production environments - [x] Verify the MR with the feature flag is merged to `master` and has been deployed to non-production environments with `/chatops gitlab run auto_deploy status <merge-commit-of-your-feature>` - [x] Enable the feature globally on non-production environments with `/chatops gitlab run feature set ci_interpolation_split_function true --dev --pre --staging --staging-ref` - [x] Verify that the feature works as expected in staging-canary ### Specific rollout on production For visibility, all `/chatops` commands that target production must be executed in the [`#production` Slack channel](https://gitlab.slack.com/archives/C101F3796) and cross-posted (with the command results) to the responsible team's Slack channel. - [x] Ensure that the feature MRs have been deployed to both production and canary with `/chatops gitlab run auto_deploy status <merge-commit-of-your-feature>` - [x] Incrementally roll out the feature on production: - `/chatops gitlab run feature set ci_interpolation_split_function 10 --actors` - Monitor for 1 hour - `/chatops gitlab run feature set ci_interpolation_split_function 25 --actors` - Monitor for 1 hour - `/chatops gitlab run feature set ci_interpolation_split_function 50 --actors` - Monitor for 1 hour - `/chatops gitlab run feature set ci_interpolation_split_function 100 --actors` - [x] After 100% enabled, wait at least one day before cleanup ### Release the feature - [x] Create a merge request to remove the `ci_interpolation_split_function` feature flag - [x] Clean up the feature flag from all environments: `/chatops gitlab run feature delete ci_interpolation_split_function --dev --pre --staging --staging-ref --production` - [x] Close the feature issue - [x] Close this rollout issue ## Rollback Steps - [ ] Disable on production: `/chatops gitlab run feature set ci_interpolation_split_function false` - [ ] Disable on non-production: `/chatops gitlab run feature set ci_interpolation_split_function false --dev --pre --staging --staging-ref`

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