This also required adding support for calculating the metadata version
based on the protocol version, and sending the current protocol version
to the server as a hint.

When the identity provider does not provide a validity of the credentials, the Java implementation takes now + 6 months while we took now + 52/2 weeks, which is not always the same. This commit takes the approach of the Java implementation.

The struct name now matches exactly (up to idiomatic spelling differences)
with the name of the folder that it parses and updates.