add filter to append extra fields during fields render

Hello,

First, thank you for this plugin , it’s been very helpful.

One feature I find missing is the ability to customize form field values before they are rendered in the admin detail view.

Use case example:
Suppose we have a form field that stores a post_id. During render, we may want to append another field showing the corresponding post title, e.g. post_title: get_the_title( $id ).

Currently, this requires editing the plugin core. For example, in inc/admin-form-details.php 46:

$form_data  = unserialize( $results[0]->form_value );

// Adding a filterable variable so $form_data remains untouched
$fields = apply_filters( 'cfdb7_form_fields', $form_data, $this->form_post_id );

// Using $fields variable to render fields
foreach ( $fields as $key => $data ):

And in functions.php, we could then extend the data safely:

add_filter( 'cfdb7_form_fields', function( $data, $form_post_id ) {
    if ( $form_post_id !== 300 ) return $data;

    $data['test_field'] = 'test value';
    return $data;
}, 10, 2 );

Thank you!