Fix remote execution bug where email address can contain malicious code

also convert almost all cmd execs for certificates to properly escape arguments

backend/schema/common.json

@@ -110,6 +110,11 @@
 		"caching_enabled": {
 			"description": "Should we cache assets",
 			"type": "boolean"
+		},
+		"email": {
+			"description": "Email address",
+			"type": "string",
+			"pattern": "^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}$"
 		}
 	}
 }