I have a fun experiment for OP, since you already walked the reverse engineering route.

Why not download the most popular DAV libraries from various languages, Java, C++, PHP, etc. Regardless how ancient they are.

And then have AI like Claude to analyze and bring in the improvements to your own Go library?

I was doing something like that for Kerberos and Iceberg Rest Catalog API, until I got distracted and moved on to other things.