Enhance to_zpl Method to Support Individual ZPL Commands for Each Page

[Federaffo]

Description:

This PR introduces the ability to wrap each PDF page with its own set of ZPL start (^XA) and end (^XZ) commands when converting PDF pages to ZPL format. This feature is controlled by the split_page attribute, allowing each page to be treated as a separate print job if required. This update provides greater flexibility in handling multi-page PDFs, especially useful for scenarios where independent printing of each page is needed.

Changes:

• Method Update: The to_zpl method within the conversion class has been modified to check the split_page attribute. This determines whether each page's ZPL code should be individually wrapped with ^XA and ^XZ.
• Conditional Logic: Added conditional logic to either wrap each page individually or collectively, based on the self._complete_zpl and self.split_page attributes.
• Flexible Printing Option: Users can now choose to print each page as a separate job or as part of a single continuous job, enhancing the method's utility in diverse printing scenarios.

Impact:

• Usability Improvement: Makes the ZPL conversion process more versatile and applicable to a broader range of printing scenarios.
• Backward Compatibility: Default behavior remains unchanged unless the split_page attribute is explicitly set to True, ensuring that existing implementations are not affected.
• Enhanced Control: Users gain more control over how the output is handled by ZPL-compatible printers, particularly beneficial for batch printing tasks.

[miikanissi]

Thank you for the contribution!