feat: Implement invoice generation and emailing functionality

- Added invoice generation logic using DomPDF.
- Integrated invoice data retrieval from the API.
- Implemented language determination for invoices based on customer data.
- Added options to email invoices to customers and admin.
- Included HTML output option for direct viewing in the browser.
- Ensured proper redirection and error handling throughout the process.

settings/translations/translations_US.php

@@ -336,8 +336,8 @@ $softwaretool_step_2 = 'Press "<i>connect</i>" button"';
 $softwaretool_step_3 = 'A popup will appear asking to select a device. Select the device by clicking on it and the press the connect button.';
 $softwaretool_step_4 = 'After pop-up disappears the device will be read, status bar will show progress';
 $softwaretool_step_5 = 'Available software upgrades will be displayed with Name, Description and Price';
-$softwaretool_step_6 = 'Select a free upgrade (price = 0) to download and install';
-$softwaretool_step_7 = 'For paid upgrades, please contact support';
+$softwaretool_step_6 = 'Select a software version';
+$softwaretool_step_7 = 'For paid upgrades, please follow the payment process';
 $softwaretool_step_8 = '<b>Be aware: This process cannot be stopped and needs to finish.</b>';
 $softwaretool_no_updates = 'No software updates found';
 $softwaretool_checking = 'Checking for software updates...';