Fix forward_scheme validation in Redirection Host

Should solve error `data/forward_scheme must be equal to one of the allowed values` when configuring a Redirection Host with scheme set to `auto`. #4074

Author: Nephiel

backend/schema/components/redirection-host-object.json

@@ -28,7 +28,7 @@
 		},
 		"forward_scheme": {
 			"type": "string",
-			"enum": ["http", "https"]
+			"enum": ["auto", "http", "https"]
 		},
 		"forward_domain_name": {
 			"description": "Domain Name",