ext_tables.php

<?php
defined('TYPO3_MODE') || die('Access denied.');

call_user_func(
  function()
  {

    \TYPO3\CMS\Extbase\Utility\ExtensionUtility::registerPlugin(
      'Dnilabs.DnilabsPetition',
      'Petition',
      'Petition'
    );
    \TYPO3\CMS\Extbase\Utility\ExtensionUtility::registerPlugin(
      'Dnilabs.DnilabsPetition',
      'Activation',
      'Activation'
    );

    \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addStaticFile('dnilabs_petition', 'Configuration/TypoScript', 'dnilabs petition');

    \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addLLrefForTCAdescr('tx_dnilabspetition_domain_model_petition', 'EXT:dnilabs_petition/Resources/Private/Language/locallang_csh_tx_dnilabspetition_domain_model_petition.xlf');
    \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::allowTableOnStandardPages('tx_dnilabspetition_domain_model_petition');

    \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addLLrefForTCAdescr('tx_dnilabspetition_domain_model_participant', 'EXT:dnilabs_petition/Resources/Private/Language/locallang_csh_tx_dnilabspetition_domain_model_participant.xlf');
    \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::allowTableOnStandardPages('tx_dnilabspetition_domain_model_participant');


  }
);
$extensionName = strtolower(\TYPO3\CMS\Core\Utility\GeneralUtility::underscoredToUpperCamelCase($_EXTKEY));
$pluginName = strtolower('Petition');
$pluginSignature = $extensionName.'_'.$pluginName;
$TCA['tt_content']['types']['list']['subtypes_excludelist'][$pluginSignature] = 'layout,select_key,pages';
$TCA['tt_content']['types']['list']['subtypes_addlist'][$pluginSignature] = 'pi_flexform';
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addPiFlexFormValue($pluginSignature, 'FILE:EXT:'.$_EXTKEY . '/Configuration/FlexForms/petition.xml');