Add krbPrincipalName as X_REMOTE_USER_PRINCIPAL for httpd

We only set this for usage through sssd and httpd but this could be used as the
de facto standard for all httpd based identity providers.

Follow up to:
ManageIQ/manageiq#23723
ManageIQ/manageiq-appliance#401
ManageIQ/guides#587

Author: jrafanie

manageiq-operator/api/v1alpha1/helpers/miq-components/httpd_conf.go

@@ -373,11 +373,12 @@ func httpdAuthApplicationAPIConf(authType, authName, extraConfig string, enableL
 func httpdAuthLookupUserDetailsConf() string {
 	return `
 <LocationMatch ^/dashboard/external_authenticate$|^/dashboard/kerberos_authenticate$|^/api>
-	LookupUserAttr mail        REMOTE_USER_EMAIL
-	LookupUserAttr givenname   REMOTE_USER_FIRSTNAME
-	LookupUserAttr sn          REMOTE_USER_LASTNAME
-	LookupUserAttr displayname REMOTE_USER_FULLNAME
-	LookupUserAttr domainname  REMOTE_USER_DOMAIN
+	LookupUserAttr mail             REMOTE_USER_EMAIL
+	LookupUserAttr givenname        REMOTE_USER_FIRSTNAME
+	LookupUserAttr sn               REMOTE_USER_LASTNAME
+	LookupUserAttr displayname      REMOTE_USER_FULLNAME
+	LookupUserAttr domainname       REMOTE_USER_DOMAIN
+	LookupUserAttr krbPrincipalName REMOTE_USER_PRINCIPAL
 
 	LookupUserGroups           REMOTE_USER_GROUPS ":"
 	LookupDbusTimeout          5000
@@ -401,6 +402,7 @@ RequestHeader set X_REMOTE_USER_FULLNAME        %%{REMOTE_USER_FULLNAME}e  env=R
 RequestHeader set X_REMOTE_USER_GROUPS          %%{REMOTE_USER_GROUPS}e    env=REMOTE_USER_GROUPS
 RequestHeader set X_REMOTE_USER_GROUP_DELIMITER "%s"
 RequestHeader set X_REMOTE_USER_DOMAIN          %%{REMOTE_USER_DOMAIN}e    env=REMOTE_USER_DOMAIN
+RequestHeader set X_REMOTE_USER_PRINCIPAL       %%{REMOTE_USER_PRINCIPAL}e env=REMOTE_USER_PRINCIPAL
 `
 	return fmt.Sprintf(s, delimiter)
 }