Ok, so I figured out that the line:
ovirt.engine.aaa.authn.mapping.plugin = mapping
should go to:
/etc/ovirt-engine/extensions.d/corp.mydomain.com-authn.properties
Now when I run:
ovirt-engine-extensions-tool --log-level=FINEST aaa login-user --profile=corp.mydomain.com
--user-name=a_user
I get INVALID_CREDENTIALS although user and password are correct:
diagnosticMessage = 80090308: LdapErr: DSID-0C09042F, comment: AcceptSecurityContext
error, data 52e, v2580