Add barcode support

[correa]

Using the same mechanism as KDChart It should be possible to add barcode support using KDE Framework's Prison library.

Would such patches be acceptable?

[dfaure-kdab]

I'm worried about KDReports ending up with 100 dependencies, if it's all implemented as shared libs to link to.
Optional dependencies, of course, but this still means enabling all of them when working on KDReports (and in CI) to make sure all of the code works.

Solution 1: providing the barcode as a QPixmap. But this leads to problems with printing high-definition, I think.
Solution 2: creating a plugin mechanism. But then something somewhere still needs to depend on both KDReports and Prison anyway.
Solution 3: does Prison provide something scalable, like maybe a SVG, or drawing into a QPicture? Maybe we could use QPicture as the exchange format between the two, and then the app code can directly "connect" the two without the need for prison-specific code in KDReports.

[correa]

Plugins could be a way. IMHO to be usefull reports must be user extensible, which means the barcode should also be available in the XML parser. On the other hand I guess there aren't that many possible elements one could wish in a report. There is already text, tables, and charts. Of the common elements only barcodes is missing. The tables could really see improvements with SUMs and grouping but that probably wouldn't be an external dependency.

Is CI run internally or could it run from github actions? If it's run from github actions new dependency patches could require the CI changes as well.

[dfaure-kdab]

Sum and grouping sound like jobs for proxymodels anyway, those can be provided externally :)

The CI is KDAB-internal at the moment, we'll handle it if necessary, no big deal.

However solution 3 still sounds best to me?