docs: update Redis deployment guidance

[miachillgood]

Applicable spec: N/A — documentation correction tracked by #782

Overview

Updates the tutorial and integration reference to deploy one redis-k8s application and integrate it once with Indico. That matches the charm's single Redis relation and the current integration tests.

Closes #782

Rationale

The documentation still instructed users to deploy separate redis-broker and redis-cache applications. Following those steps conflicts with the current charm interface and causes the tutorial to diverge from tested deployment behavior.

Juju Events Changes

None.

Module Changes

None.

Library Changes

None.

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation for charmhub is updated
• A change artifact was added for user-relevant changes in docs/release-notes/artifacts. If this PR does not require a change artifact, the PR has been tagged with no-release-note.
• The PR is tagged with appropriate label (urgent, trivial, complex)
• The changelog is updated with user-relevant changes in the format of keep a changelog v1.1.0

ISD054 does not apply because there are no charm-code changes. This is a focused correction already categorized as trivial and no-release-note on #782; maintainers can apply the corresponding PR labels. No changelog or change artifact is needed for the documentation-only correction.

Validation performed:

• Confirmed charmcraft.yaml exposes one Redis relation with limit 1
• Confirmed integration tests deploy and integrate one Redis application
• Confirmed the updated pages contain no remaining redis-broker or redis-cache instructions
• Ran git diff --check

[erinecon]

Thank you so much for updating our documentation 🎉 I spotted a nit and also ran into an issue when trying out the tutorial myself

[erinecon]

Suggested change

	Since Indico requires connections to PostgreSQL and Redis, you'll deploy them too. A single Redis application provides both caching and the Celery message broker. For more information, see [Charm Architecture](https://charmhub.io/indico/docs/explanation-charm-architecture).
	Indico requires connections to PostgreSQL and Redis. A single Redis application provides both caching and the Celery message broker. For more information, see [Charm Architecture](https://charmhub.io/indico/docs/explanation-charm-architecture).

nit, for conciseness

[erinecon]

I ran into an error when trying this command:

ubuntu@charm-tutorial-vm:~$ juju integrate indico redis-k8s
ERROR ambiguous relation: "indico redis-k8s" could refer to "indico:redis-broker redis-k8s:redis"; "indico:redis-cache redis-k8s:redis"

So I think we still need two juju integrate commands, but for a single redis-k8s charm:

Suggested change

	juju integrate indico redis-k8s
	juju integrate indico:redis-broker redis-k8s
	juju integrate indico:redis-cache redis-k8s

command --> commands in the text above, and if you want, you could also add some text pointing out that we must explicitly use two different relation endpoints so that the Redis charm can provide both capabilities.

[erinecon]

Hi @miachillgood , thanks for opening this PR! I just noticed that your commit is not signed. This is a requirement for merging PRs into this repository (see the contributing guidelines).

You'll either need to retroactively sign your commits in this PR, or close the PR and reopen with signed commits. Please let me know if you need any help or have any questions!