Canonical observability stack abbreviated

*Please describe the question or issue you're facing with "How to integrate with COS - WordPress charm documentation".*

I am a newcomer and the meaning of COS could be quite confusing. A linked URL could be helpful for more context.

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*Reported from: https://canonical.com/juju/docs/wordpress-k8s-charm/latest/how-to/integrate-with-cos/*

Start with the reported documentation page at https://canonical.com/juju/docs/wordpress-k8s-charm/latest/how-to/integrate-with-cos/ and find the first use of “COS.” Clarify the abbreviation and add a useful context link, then verify the rendered page makes the term understandable to newcomers.

Written by the indexing model from the issue text.