docs: migrate URL

[erinecon]

What this PR does

This PR migrates the RTD documentation under the Canonical domain.

Why we need it

URL migrations are a high priority this cycle that we need to complete ASAP.

Checklist

• I followed the contributing guide
• I added or updated the documentation (if applicable)
• I updated docs/changelog.md with user-relevant changes
• I added a change artifact for user-relevant changes in docs/release-notes/artifacts. If no change artifact is necessary, I tagged the PR with the label no-release-note.
• I used AI to assist with preparing this PR
• [N/A] I added or updated tests as needed (unit and integration)
• [N/A] If integration test modules are used: I updated the workflow configuration
  (e.g., in .github/workflows/integration_tests.yaml, ensure the modules list is correct)
• [N/A] If this PR involves Terraform: terraform fmt passes and tflint reports no errors
• [N/A] If this PR involves Rockcraft: I updated the version

[Copilot]

Pull request overview

Note

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Migrates HAProxy charm documentation references from Read the Docs/Ubuntu domains to the Canonical domain, and updates Sphinx configuration/assets to publish with the new canonical URL.

Changes:

• Updated multiple charmcraft.yaml files to point links.documentation to https://canonical.com/juju/docs/haproxy-charm/.
• Updated Sphinx config (docs/conf.py) to use Canonical-domain base URLs and load a new JS file.
• Added a small JS helper to rewrite old RTD-domain links in rendered docs; refresh README + changelog entry.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
haproxy-spoe-auth-operator/charmcraft.yaml	Points charm metadata documentation link to Canonical domain
haproxy-route-policy-operator/charmcraft.yaml	Points charm metadata documentation link to Canonical domain
haproxy-operator/charmcraft.yaml	Points charm metadata documentation link to Canonical domain
haproxy-ddos-protection-configurator/charmcraft.yaml	Updates documentation link target (but currently retains questionable YAML structure)
docs/conf.py	Sets canonical/base URLs for Sphinx outputs and includes new JS asset
docs/changelog.md	Adds changelog entry for the migration
docs/_static/js/overwrite_links.js	New script to rewrite old-domain links in rendered docs
README.md	Updates documentation location and link