Thanks for the feedback!
Indeed, I had in mind the usual HTTP 201 for creation, and so on for other cases, but definitely this needed to be not just in my mind. That's the whole point.
Also, your challenge here made me rethink and refactor the prototype to avoid sending back the log as it's usually done in REST endpoints, because it seems like a waste when for instance client would be sending 5000 characters or more to just have them transiting back and forth for nothing.
About the authentication/registration, I clarified the intent is to make this endpoint /behind/ what's defined in JEP 303.
Yes, let's meet when you're available, I think that's a good idea. I'm especially interested to hear if you have an opinion about what the response payload should have.
For instance, as I wrote in a comment in the JEP:
"Should we compute a hash or something to be able to uniquely reference/find a log in the system between client and server if needed?"
-- Baptiste