[MM-20061] Add System Admin filter to both LDAP and SAML (#13534)

* promote user to admin upon login

* Add SAML support for admin accounts

* update en.json

* update i18n

* Add tests as per comments

* change function name

* fix config.go

* invalidate cache so its not checking for cache when roles change

* add enable attribute and filter

model/user.go

@@ -633,6 +633,10 @@ func (u *User) IsGuest() bool {
 	return IsInRole(u.Roles, SYSTEM_GUEST_ROLE_ID)
 }
 
+func (u *User) IsSystemAdmin() bool {
+	return IsInRole(u.Roles, SYSTEM_ADMIN_ROLE_ID)
+}
+
 // Make sure you acually want to use this function. In context.go there are functions to check permissions
 // This function should not be used to check permissions.
 func (u *User) IsInRole(inRole string) bool {