domain.com/dashboard
domain.com/projects
domain.com/project/100
domain.com/project/100/emails
domain.com/project/100/email/3210
domain.com/project/100/files
domain.com/project/100/file/56968

Route::group(['prefix' => 'project'], function(){
  Route::group(['prefix' => '{project_id}'], function($project_id){

    // Files
    Route::resource('files', 'FileController');

  });
});