We currently parse the authMechanismProperties, including the SERVICE_REALM property, but don't actually use that value directly in the kerberos module. We still have cross-realm support through the user principal, but should also support this explicit method.

Impact on the shell:

• required to comply with the connection uri format (?authMechanismProperties=SERVICE_REALM:servicename)
• required to implement the sspiRealmOverride option for the GSSAPI auth mechanism