qgswfsgetfeature: Do not invert axis if no SRSNAME is passed

A WFS request such as
`SERVICE=WFS&REQUEST=GetFeature&VERSION=1.1.0&SRSNAME=EPSG:4326` does
not invert the axis and return the coordinates in the LON/LAT
order. For example:

<gml:Envelope srsName="EPSG:4326">
  <gml:lowerCorner>2.358 48.865</gml:lowerCorner>
  <gml:upperCorner>2.37 48.876</gml:upperCorner>
</gml:Envelope>

However, the same request without a SRSNAME parameter inverts the axis
and returns the the coordinates in the LAT/LON order:

<gml:Envelope srsName="EPSG:4326">
  <gml:lowerCorner>48.865 2.358</gml:lowerCorner>
  <gml:upperCorner>48.876 2.37</gml:upperCorner>
</gml:Envelope>

With this change, the axis is not inverted if the SRSNAME parameter is
not passed and has the same behavior as `SRSNAME=EPSG:4326`.

This is a follow-up of qgis#45270.

src/server/services/wfs/qgswfsgetfeature.cpp

@@ -464,7 +464,8 @@ namespace QgsWfs
         const QString srsName {request.serverParameters().value( QStringLiteral( "SRSNAME" ) )};
         const bool invertAxis { mWfsParameters.versionAsNumber() >= QgsProjectVersion( 1, 1, 0 ) &&
                                 outputCrs.hasAxisInverted() &&
-                                ! srsName.startsWith( QLatin1String( "EPSG:" ) ) };
+                                ! srsName.startsWith( QLatin1String( "EPSG:" ) ) &&
+                                !srsName.isEmpty() };
 
         const createFeatureParams cfp = { layerPrecision,
                                           layerCrs,
@@ -1251,7 +1252,8 @@ namespace QgsWfs
           const QString srsName {request.serverParameters().value( QStringLiteral( "SRSNAME" ) )};
           const bool invertAxis { mWfsParameters.versionAsNumber() >= QgsProjectVersion( 1, 1, 0 ) &&
                                   crs.hasAxisInverted() &&
-                                  ! srsName.startsWith( QLatin1String( "EPSG:" ) ) };
+                                  ! srsName.startsWith( QLatin1String( "EPSG:" ) ) &&
+                                  !srsName.isEmpty() };
 
           // If requested SRS (srsName) is different from rect CRS (crs) we need to transform the envelope
           QgsCoordinateTransform transform;

tests/testdata/qgis_server/wfs_getFeature_1_1_0_featureid_0_1_1_0_srsname.txt

@@ -3,8 +3,8 @@ Content-Type: text/xml; subtype=gml/3.1.1; charset=utf-8
 <wfs:FeatureCollection xmlns:wfs="http://www.opengis.net/wfs" xmlns:ogc="http://www.opengis.net/ogc" xmlns:gml="http://www.opengis.net/gml" xmlns:ows="http://www.opengis.net/ows" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:qgs="http://www.qgis.org/gml" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/wfs http://schemas.opengis.net/wfs/1.1.0/wfs.xsd http://www.qgis.org/gml ?MAP=/home/etienne/dev/qgis/qgis-master/tests/testdata/qgis_server/test_project_wfs.qgs&amp;SERVICE=WFS&amp;VERSION=1.1.0&amp;REQUEST=DescribeFeatureType&amp;TYPENAME=testlayer&amp;OUTPUTFORMAT=text/xml; subtype%3Dgml/3.1.1">
 <gml:boundedBy>
  <gml:Envelope srsName="EPSG:4326">
-  <gml:lowerCorner>44.90139484 8.20345931</gml:lowerCorner>
-  <gml:upperCorner>44.90148253 8.20354699</gml:upperCorner>
+  <gml:lowerCorner>8.20345931 44.90139484</gml:lowerCorner>
+  <gml:upperCorner>8.20354699 44.90148253</gml:upperCorner>
  </gml:Envelope>
 </gml:boundedBy>
 <gml:featureMember>
@@ -13,11 +13,13 @@ Content-Type: text/xml; subtype=gml/3.1.1; charset=utf-8
    <gml:Envelope srsName="EPSG:4326">
     <gml:lowerCorner>44.90148253 8.20349634</gml:lowerCorner>
     <gml:upperCorner>44.90148253 8.20349634</gml:upperCorner>
+    <gml:lowerCorner>8.20349634 44.90148253</gml:lowerCorner>
+    <gml:upperCorner>8.20349634 44.90148253</gml:upperCorner>
    </gml:Envelope>
   </gml:boundedBy>
   <qgs:geometry>
    <Point xmlns="http://www.opengis.net/gml" srsName="EPSG:4326">
-    <pos xmlns="http://www.opengis.net/gml" srsDimension="2">44.90148253 8.20349634</pos>
+    <pos xmlns="http://www.opengis.net/gml" srsDimension="2">8.20349634 44.90148253</pos>
    </Point>
   </qgs:geometry>
   <qgs:id>1</qgs:id>