Measure latency of the authentication requests (only the ones where we
actually perform encryption).

This should make the server code more readable by disentangling it
from the backend implementation.

This first version (with tests) only supports the SQLite driver.

It wasn't updated after the config refactoring.

Avoid implementing our own version of asp/userenckey/u2f serialization
and deserialization.

Add filter to report last login information for a service to usermetadb.

The filter is active when the `enable_last_login_reporting` option is
set.
Signed-off-by: shammash <shammash@autistici.org>

Allows us to use rc.d-style setup where later files override contents
from previous ones, useful in a configuration management context.

Move from Config-objects-with-private-members to a full separation of
configuration and runtime types, which simplifies a lot of interface
boundaries between different parts of the code.

More specifically, the Server is a lot leaner and its functionality is
clearer. Backends also have a slightly improved interface.

With proper DN escaping.

Meant to integrate well with DNS-based service discovery: the client
will constantly monitor the DNS results for changes, and dynamically
modify the list of memcache backends.

This makes it possible to run the auth-server more easily for smaller
projects.

Add the related documentation to the README. Include a nullU2FStorage
handler to prevent nil pointer dereferences in U2F code.

Backed by memcache, like the U2F challenge storage. The code has been
refactored to abstract the common replicated memcache client away.

Plus a couple of lint style fixes.

Backed by one or more replicated memcached instances.

Introduces the *services_dir* configuration parameter.