Sanitize username for ABAC.
Sanitize username for ABAC.

ABAC limits names to alphanumeric (plus underscore). Sanitize the name
by eliminating non-alphanumeric, non-underscore characters. Then the
username can be used as the common name (--cn) in the ABAC ID
certificate.

tcmitchell/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal