Warn about clear paths with Server Side Encryption (SSE)

[Toorero]

As suggested by me in nextcloud/server#55393 there should be a red warning banner in Server-side encryption configuration warning about the potential danger that filenames and paths to files are left unencrypted.

I think just mentioning it in the running text, without the danger associated with it, doesn't really cut it.

[joshtrichards]

Hi @Toorero - Thanks for the feedback.

I've been working on a first pass rewrite of the main SSE chapter in the Admin Manual. While not specifically targeting your suggestion, you may be interested in it: initial draft is in #13754

[Toorero]

This looks great 👍🏻. Thanks for your rework work and for putting my suggestion in the docs.