Allow setting sourceProject on groups

[u-cav]

Description

Related to #601.

It is now possible to correctly set sourceRepository, thanks!
SourceProject is automatically shown for embedded layers, but does not seem to be saved in the cfg. It is not possible to manually specify the sourceProject:

This makes total sense for layers, but for groups where groupAsLayer is true setting the sourceProject enables Lizmap to use the shared cache.

Setting this manually in the cfg works correctly, and the shared cache is used.

Enabling the field SourceProject for groups would enable users to use a centralized cache for the tiled baselayers where multiple layers are grouped as one.

CC: @mind84

Context

• Lizmap Web Client : 3.8.3
• Lizmap plugin : 4.4.4
• QGIS Desktop : 3.34.3
• QGIS Server : 3.34.12
• Py-QGIS-Server : 1.9.2
• QGIS Server plugin atlasprint : 3.4.1
• QGIS Server plugin lizmap_server : 2.11.2
• QGIS Server plugin wfsOutputExtension : 1.8.2

[github-actions]

Hiya!
This issue has gone quiet. 👻
We get a few issues, so we currently close issues after 60 days of inactivity.
If we missed this issue or if you want to keep it open, please reply here.
As a friendly reminder: the best way to see this issue, or any other, fixed is to open a Pull Request.
Thanks for being a part of the Lizmap community! 🦎

[cfsgarcia]

Hi,
It doesn't seem possible to set embedded layers and groups "source project" in the qGIS Lizmap plugin.

https://github.com/3liz/lizmap-plugin/blob/master/lizmap/plugin.py
line 2154:
if self.embeddedGroups and item_key in self.embeddedGroups:

self.embeddedGroups is a constant set to None.

What is the reason for that?