feat(Sales Invoice): Convert the PDF data to PDF/A-3 using ghostscript.

[timschneider]

Convert PDF to PDF/A-3 if ghostscript is installed.
Fail on error and do not output pdf/a-3 data with xml data, erpnext will output the default pdf.

The switch "-dPDFACompatibilityPolicy=1", will behave like

PDFACompatibilityPolicy integer

    When an operation (e.g. pdfmark) is encountered which cannot be emitted in a PDF/A compliant file, this policy is consulted, there are currently three possible values:

    0 - (default) Include the feature or operation in the output file, the file will not be PDF/A compliant. Because the document Catalog is emitted before this is encountered, the file will still contain PDF/A metadata but will not be compliant. A warning will be emitted in this case.

    1 - The feature or operation is ignored, the resulting PDF file will be PDF/A compliant. A warning will be emitted for every elided feature.

    2 - Processing of the file is aborted with an error, the exact error may vary depending on the nature of the PDF/A incompatibility.

Maybe change it later to 2 or make it configurable.

[0xD0M1M0]

Does Ghostscript needs to be added to pyprojects.toml so it can be installed as dependency?

[timschneider]

@0xD0M1M0

Does Ghostscript needs to be added to pyprojects.toml so it can be installed as dependency?

I don't know if it is possible to add an external dependency to the pyproject.toml that will be installed with the plugin.