code: public void deleteUser(Object userIdOrUsername, Boolean hardDelete) throws GitLabApiException {
          GitLabApiForm formData = new GitLabApiForm().withParam("hard_delete ", hardDelete);
          Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
          delete(expectedStatus, formData.asMap(), "users", getUserIdOrUsername(userIdOrUsername));
      }
docs: Deletes a user. Available only for administrators.
  
  <pre><code>GitLab Endpoint: DELETE /users/:id</code></pre>
  
  @param userIdOrUsername the user in the form of an Integer(ID), String(username), or User instance
  @param hardDelete If true, contributions that would usually be moved to the
  ghost user will be deleted instead, as well as groups owned solely by this user
  @throws GitLabApiException if any exception occurs