code: public String getId() {
          String id = operation.getOperationId();
  
          if (id == null)
              id = getPath() + " " + getMethod().toString().toLowerCase();
  
          return id;
      }
docs: Returns an unique id for the operation.<br>
  Use {@code <operation id>}, then {@code <operation path> lowercase(<operation method>)} if operation id is not set.
  
  @return operation unique id