Handle cookie banner origin validation + unicity

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/validator/validator_format.go

@@ -133,6 +133,49 @@ func GID(entityTypes ...uint16) ValidatorFunc {
 	}
 }
 
+// Origin validates that a string is a valid web origin (scheme + host + optional port).
+// No path, query, fragment, or userinfo is allowed.
+func Origin() ValidatorFunc {
+	return func(value any) *ValidationError {
+		actualValue, isNil := dereferenceValue(value)
+		if isNil {
+			return nil
+		}
+
+		str, ok := actualValue.(string)
+		if !ok {
+			return newValidationError(ErrorCodeInvalidFormat, "value must be a string")
+		}
+
+		if str == "" {
+			return nil
+		}
+
+		parsedURL, err := url.Parse(str)
+		if err != nil {
+			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
+		}
+
+		if parsedURL.Scheme != "http" && parsedURL.Scheme != "https" {
+			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
+		}
+
+		if parsedURL.Host == "" {
+			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
+		}
+
+		if parsedURL.Path != "" && parsedURL.Path != "/" {
+			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
+		}
+
+		if parsedURL.RawQuery != "" || parsedURL.Fragment != "" || parsedURL.User != nil {
+			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
+		}
+
+		return nil
+	}
+}
+
 // Domain validates that a string is a valid domain name.
 func Domain() ValidatorFunc {
 	return func(value any) *ValidationError {