Added alias resolution for PlantUML annotations

src/util/error.h

@@ -20,10 +20,18 @@
 #include <stdexcept>
 
 namespace clanguml::error {
+
 struct uml_alias_missing : public virtual std::runtime_error {
     uml_alias_missing(const std::string &message)
         : std::runtime_error(message)
     {
     }
 };
+
+struct substring_delimiter_not_found : public virtual std::runtime_error {
+    substring_delimiter_not_found(const std::string &message)
+        : std::runtime_error(message)
+    {
+    }
+};
 }