fix: update docs and on ssl endpoint (#592)

I added more information to provisionSiteTLSCertificate because it had a
confusing error message. This should help clarify our users. I also
changed the error message to be more informative.

This should help bolt

<img width="910" height="493" alt="image"
src="https://github.com/user-attachments/assets/151fdcfa-621d-4185-b2bc-bdd16b63fad9"
/>

Author: khendrikse