Fixed mermaid verbatim directives handling

src/sequence_diagram/generators/mermaid/sequence_diagram_generator.cc

@@ -48,6 +48,11 @@ generator::generator(
 {
 }
 
+void generator::generate_diagram_type(std::ostream &ostr) const
+{
+    ostr << "sequenceDiagram\n";
+}
+
 void generator::generate_call(const message &m, std::ostream &ostr) const
 {
     const auto &from = model().get_participant<model::participant>(m.from());
@@ -389,8 +394,6 @@ void generator::generate_diagram(std::ostream &ostr) const
 {
     model().print();
 
-    ostr << "sequenceDiagram\n";
-
     if (config().participants_order.has_value) {
         for (const auto &p : config().participants_order()) {
             LOG_DBG("Pregenerating participant {}", p);

src/sequence_diagram/generators/mermaid/sequence_diagram_generator.h

@@ -60,6 +60,13 @@ public:
      */
     void generate_diagram(std::ostream &ostr) const override;
 
+    /**
+     * @brief Generate the diagram type
+     *
+     * @param ostr Output stream
+     */
+    void generate_diagram_type(std::ostream &ostr) const override;
+
     /**
      * @brief Generate sequence diagram message.
      *