Change the backend for xlsformconverter to use the new convert2json library

[suricactus]

Instead of directly parsing and converting the xlsform into a QGIS project, we add an intermediate step:

1. xlsform - parse and convert to an abstract JSON representation
2. json - get the abstract JSON representation and converts it to an actual QGIS project with all it's files

The xlsforms2qgis library will be retired and convert2qgis is going to take care of the conversion. We eventually publish it even to pypi.

See https://github.com/opengisch/convert2qgis

[nirvn]

@suricactus , let me know when you want me to review / test this.

[suricactus]

Not yet, needs a bit more love and polishing. But we are close!

[suricactus]

@nirvn ready for review of the current state of the PR.

[nirvn]

@suricactus , looking at this now.

[nirvn]

Hitting this bug when trying the alg on QGIS 4:

~~~~~~~~~~~~~~~~~~~~^^
File "/home/webmaster/.local/share/QGIS/QGIS4/profiles/default/python/plugins/xlsformconverter/convert2qgis_c2d491e9552d44132bc42edcab8eeecc09a087c2.whl/convert2qgis/json2qgis/json2qgis.py", line 118, in _create_project
self._create_layer(dataset_def)
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
File "/home/webmaster/.local/share/QGIS/QGIS4/profiles/default/python/plugins/xlsformconverter/convert2qgis_c2d491e9552d44132bc42edcab8eeecc09a087c2.whl/convert2qgis/json2qgis/json2qgis.py", line 285, in _create_layer
layer.setFlags(get_layer_flags(layer.flags(), dataset_def))
~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: QgsMapLayer.setFlags(): argument 1 has unexpected type 'int'

[suricactus]

@nirvn xlsform file will be helpful. Do you reproduce this on 3.x?

[nirvn]

@suricactus , it's fine with QGIS 3.X

[suricactus]

Hitting this bug when trying the alg on QGIS 4:

~~~~~~~~~~~~~~~~~~~~^^
File "/home/webmaster/.local/share/QGIS/QGIS4/profiles/default/python/plugins/xlsformconverter/convert2qgis_c2d491e9552d44132bc42edcab8eeecc09a087c2.whl/convert2qgis/json2qgis/json2qgis.py", line 118, in _create_project
self._create_layer(dataset_def)
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
File "/home/webmaster/.local/share/QGIS/QGIS4/profiles/default/python/plugins/xlsformconverter/convert2qgis_c2d491e9552d44132bc42edcab8eeecc09a087c2.whl/convert2qgis/json2qgis/json2qgis.py", line 285, in _create_layer
layer.setFlags(get_layer_flags(layer.flags(), dataset_def))
~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: QgsMapLayer.setFlags(): argument 1 has unexpected type 'int'

> l = iface.activeLayer()
> flags = l.flags()
> l.setFlags(flags & QgsMapLayer.LayerFlag.Identifiable)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: QgsMapLayer.setFlags(): argument 1 has unexpected type 'int'
> l.setFlags(QgsMapLayer.LayerFlag(flags & QgsMapLayer.LayerFlag.Identifiable))

Fixes it. Will update accordingly.