CASA_auth_token is an authentication token infrastructure with support
for multiple authentication mechanisms with an emphasis on providing a
scalable single sign-on solution.

A key feature of CASA_auth_token is that its authentication tokens
contain identity information about the entity being authenticated. This
information is made available to the consuming services. The amount of
information contained in the tokens is configured on a per-service
basis. Because of this feature, we say that CASA_auth_token projects an
"Authenticated Identity".

The CASA_auth_token_svc is the infrastructure component responsible for
authenticating entities using the native authentication mechanism and
for issuing tokens that can later be used by applications to
authenticate the entity or services that are CASA authentication
enabled.