Creating new functionallity for an existing project under MPL 1.1

Question

I am currently developing a new functionality for an existing open-source project on GitHub (FusionPBX), and I have a question regarding licensing.

The original project contains files with the following license header:

/*
    FusionPBX
    Version: MPL 1.1

    The contents of this file are subject to the Mozilla Public License Version
    1.1 (the "License"); you may not use this file except in compliance with
    the License. You may obtain a copy of the License at
    http://www.mozilla.org/MPL/

    Software distributed under the License is distributed on an "AS IS" basis,
    WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
    for the specific language governing rights and limitations under the
    License.

    The Original Code is FusionPBX

    The Initial Developer of the Original Code is
    Mark J Crane <[email protected]>
    Copyright (C) 2013 - 2023
    All Rights Reserved.

    Contributor(s):
    Mark J Crane <[email protected]>
*/

I will not modify or copy any file, only create new ones in my project, but in order for my new function work with the software, some code will be copied such as:

//includes files
    require_once dirname(__DIR__, 2) . "/resources/require.php";
    require_once "resources/check_auth.php";

//classes and functions
    $database = new database;
    $result = $database->select($sql, $parameters, 'all');

And some code will be similar such as:

//new permissions
    if (permission_exists('my_new_permission')) {
        //access granted
    }

//sql queries
    $sql = "select contact_uuid, something_different ";
    $sql .= "from v_contact_settings ";

My project needs the original software installed for it to work since its a new functionality for it.

I have little understanding of software licensing, my research shows that MPL 1.1 is per file and if my code derives from it, I need to include it in my project too.

With this scenario a have the following questions:

Do I need to include this license on every file that has such similarities?
If so, do I just copy it at the start? Do I change anything?

Sorry if missed anything.