[Backport release-1.6] feat(bucket): add a ui flag to skip the s3manager web UI - #5146

What this PR does

Backport of #4881 to release-1.6.

The bucket-<name>-system release renders the users' credentials Secrets as well as the s3manager UI, and its install waits for the s3manager pod. When the tenant quota refuses that pod, the install times out and no user of the bucket gets credentials for 10 minutes or more. Operators who do not use the UI need the flag on 1.6 to take the pod out of that path.

The cherry-pick of 0c62bee4d (the only commit of #4881) conflicted in deployment.yaml, ingress.yaml and httproute.yaml of packages/system/bucket: main reads the tenant apex through cozy-lib.ns-host-required, which release-1.6 does not have. The resolution keeps the release-1.6 .Values._namespace.host lines and adds only the ui guard, so the templates differ from release-1.6 by exactly the {{- if .Values.ui }} / {{- end }} pair, as on main. On release-1.6 the apex was never required, so the "does not require the tenant apex" case passes trivially here.

A second commit sets _cluster: {} in the new packages/system/bucket suite: release-1.6 has no _cluster default in the chart values, and the ingress template aborts the render with index of untyped nil without it, which the other suites of this chart already work around the same way.

make -C packages/apps/bucket generate leaves no diff, twice in a row. helm unittest packages/apps/bucket: 11 passed. helm unittest packages/system/bucket: 10 passed.

Screenshots

Not a UI change: the flag removes the s3manager UI, it does not change it.

Downstream repositories

Walked the trigger map against the diff. As in #4881, a new field in packages/apps/bucket/values.schema.json reaches the Terraform provider and the hand-written Bucket page of the website; both follow-ups already exist as issues. The website issue targets content/en/docs/next/; whether the v1.6 docs get the same section is left to the docs maintainers.

• No downstream repository is affected by this change
• cozystack/website - follow-up: docs(bucket): document the ui flag website#750
• cozystack/terraform-provider-cozystack - follow-up: Model the bucket ui field terraform-provider-cozystack#71
• cozystack/ansible-cozystack - follow-up:
• cozystack/ccp - follow-up:
• cozystack/talm - follow-up:
• cozystack/cozyhr - follow-up:
• cozystack/cozy-proxy - follow-up:
• cozystack/cozystack-telemetry-server - follow-up:
• cozystack/external-apps-example - follow-up:
• cozystack/examples - follow-up:

Release note

feat(bucket): add a `ui` flag to the Bucket application. Set it to `false` to skip the s3manager web UI and its Service, Ingress or HTTPRoute, DNS name and TLS certificate. Defaults to `true`, so existing buckets are unchanged.