refactor(custom-templates): render template variables [EE-2602] (#6937)

api/http/handler/customtemplates/utils.go

@@ -0,0 +1,19 @@
+package customtemplates
+
+import (
+	"errors"
+
+	portainer "github.com/portainer/portainer/api"
+)
+
+func validateVariablesDefinitions(variables []portainer.CustomTemplateVariableDefinition) error {
+	for _, variable := range variables {
+		if variable.Name == "" {
+			return errors.New("variable name is required")
+		}
+		if variable.Label == "" {
+			return errors.New("variable label is required")
+		}
+	}
+	return nil
+}