code: public Project forkProject(Object projectIdOrPath, String namespace) throws GitLabApiException {
          GitLabApiForm formData = new GitLabApiForm().withParam("namespace", namespace, true);
          Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.CREATED);
          Response response = post(expectedStatus, formData, "projects", getProjectIdOrPath(projectIdOrPath), "fork");
          return (response.readEntity(Project.class));
      }
docs: Forks a project into the user namespace of the authenticated user or the one provided.
  The forking operation for a project is asynchronous and is completed in a background job.
  The request will return immediately.
  
  <pre><code>POST /projects/:id/fork</code></pre>
  
  @param projectIdOrPath the project in the form of an Integer(ID), String(path), or Project instance
  @param namespace path of the namespace that the project will be forked to
  @return the newly forked Project instance
  @throws GitLabApiException if any exception occurs