Version 2.9.1:
* Review the `GetLegendGraphic` request
* Fix Python error when evaluating a QGIS Expression about fields
* Return a warning icon if the layer is invalid
* Some internal code refactoring
Version 2.9.0:
* Review the GetLegendGraphic
* Discard invalid layers from Services other than WMS
* WMS GetLegendGraphic JSON: Provide Warning icon for invalid layers
* Fix wrong maptip returned in case of layer short name versus layer name
* Review logging in case of error
* Internal refactoring about tests
* For Lizmap Web Client 3.8 : Extending replaceExpressionText Request with ALL
features and GeoJSON format
* Add statistics
Version 2.8.6:
* GetFeatureInfo - Since QGIS 3.36, when reading a QGS file with an empty
string, the variable is not returned
