CXX-360 add support for authMechanismProperties

Our SASL implementation seems to only have support for SERVICE_NAME, so I left the others out. They are listed as "MAY IMPLEMENT" in the spec anyway.


Do we actually need the initializer and the set?

If we just had

const char* const kSupportedAuthMechanisms[] = {
    "SERVICE_NAME",
    // "CANONICALIZE_HOST_NAME",
    // "SERVICE_REALM"
};

Then you could just use std::count with a string comparison predicate in parseAuthMechanismProperties below.