Make OpenAI gateway endpoint public and provide full absolute URLs in docs

Summary

The OpenAI gateway endpoint should be publicly visible to all users (permission change), while authenticated users still receive role-based benefits such as a preconfigured API key in examples. The displayed URLs must be absolute full paths, consistent with the rest of the documentation, so that copying and pasting yields an instantly working system. In the example, the app-reference header should contain user-[username]-app-v-1-0-0 for authenticated users and user-app-v-13.37.0 for unauthenticated users. The example must be complete and placed on the /docs/ endpoint, providing enough information for a plug-and-play experience.

Steps to Reproduce

Not provided.

Expected Behaviour

• The OpenAI gateway endpoint is publicly accessible to all users.
• Authenticated users see examples with their own preconfigured API key and the header user-[username]-app-v-1-0-0.
• Unauthenticated users see examples with a generic API key placeholder and the header user-app-v-13.37.0.
• All URLs in the documentation are absolute full paths, consistent with the rest of the docs.
• The example on the /docs/ endpoint is complete and ready to use by copy-paste.

Actual Behaviour

Currently, the OpenAI gateway endpoint is not publicly visible, and the documentation examples may use relative paths or incomplete information, requiring manual adjustments before use.

Environment

Not provided.

Reported by retoor via DevPlace.