[CFM hat] Okay, either way you look at it, this patchset needs author work before any further review can be done. Peter has given some additional feedback on next steps, Stephen has asked for clarification on the goals of the patchset, etc. I feel pretty confident in marking this Returned with Feedback.
That makes sense. I just got back to working on this patch and am aiming to get this ready for the next commitfest. I plan to address the feedback by Peter and Jeff and come up with a use case to help clarify the goals to better answer Stephen's questions.
[dev hat] That said, I plan to do some additional dev work on top of this over the next couple of months. The ideal case would be to provide a server-only extension that provides additional features to existing clients in the wild (i.e. no client-side changes).
I'm also interested in plugging an existing 3rd-party SASL library into the client, which would help extensibility on that side.