MM-15021: Adding new builtin system schema for Guests (#10601)

* MM-15021: Adding new builtin system schema for Guests

* Fixing tests

* Setting properly the permissions

* Adding guests to sampledata

* Restrict more roles updates in the app layer for guests

* Adding comment to explain that permissions migration must go at the end

* Setting the default guest role for custom scheme during migration

* Fixing import and export

* Creating scheme guest roles on migration

* Fixing tests

* Fixing tests

* Fixing tests

model/user.go

@@ -565,6 +565,12 @@ func IsValidUserRoles(userRoles string) bool {
 	return true
 }
 
+// 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) IsGuest() bool {
+	return IsInRole(u.Roles, SYSTEM_GUEST_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 {