Extending CF7 with new feature or option from backend

extend_cf7_with_new_feature.php

<?php
function cf7_active_campaign_add_meta_boxes() {
    add_meta_box( 'cf7-active-campaign-settings', 'Active Campaign', 'cf7_active_campaign_metaboxes', '', 'form', 'low');
}
add_action( 'wpcf7_add_meta_boxes', 'cf7_active_campaign_add_meta_boxes' );

function cf7_activecampaign_add_page_panels($panels) {
    $panels['redirect-panel'] = array( 'title' => 'Active Campaign Settings', 'callback' => 'cf7_activecampaign_page_panel_meta' );
    return $panels;
}
add_action( 'wpcf7_editor_panels', 'cf7_activecampaign_add_page_panels' );

function cf7_active_campaign_metaboxes( $post ) {
		wp_nonce_field( 'cf7_active_campaign_metaboxes', 'cf7_active_campaign_metaboxes_nonce' );
		$cf7_activecampaing_page = get_post_meta( $post->id(), '_cf7_activecampaing_page_key', true );
		echo '<label>Test field</label>';
		echo '<input id="field1" type="text" name="field1" value="'.$cf7_activecampaing_page.'">';
}

function cf7_activecampaign_page_panel_meta( $post ) {
		wp_nonce_field( 'cf7_active_campaign_metaboxes', 'cf7_active_campaign_metaboxes_nonce' );
    $cf7_activecampaing_page = get_post_meta( $post->id(), '_cf7_activecampaing_page_key', true );
		echo '<label>Test field</label>';
		echo '<input id="field1" type="text" name="field1" value="'.$cf7_activecampaing_page.'">';
}

function cf7_activecampaign_save_contact_form( $contact_form ) {
    $contact_form_id = $contact_form->id();

    if ( !isset( $_POST ) || empty( $_POST ) || !isset( $_POST['field1'] ) ) {
        return;
    }
    else {
        if ( ! wp_verify_nonce( $_POST['cf7_active_campaign_metaboxes_nonce'], 'cf7_active_campaign_metaboxes' ) ) {
            return;
        }
        update_post_meta( $contact_form_id, '_cf7_activecampaing_page_key', $_POST['field1'] );
    }
}
add_action( 'wpcf7_after_save', 'cf7_activecampaign_save_contact_form' );

//Kada se submituje forma
function cf7_active_campaign_form_submitted( $contact_form ) {
    $contact_form_id = $contact_form->id();

    $active_campaign = get_post_meta( $contact_form_id, '_cf7_activecampaing_page_key', true );
    if ( !empty($active_campaign) ) {
      //Ovde stavi to sto treba da radi sa ActiveCampaing
    }
}
add_action( 'wpcf7_mail_sent', 'cf7_active_campaign_form_submitted' );