Add coordinate transform context to data provider options

First step to pass the context down into the rabbit hole.

Author: elpaso

python/core/auto_generated/qgsdataprovider.sip.in

@@ -58,7 +58,7 @@ Abstract base class for spatial data provider implementations.
 
     struct ProviderOptions
     {
-      int unused; //!< @todo remove me once there are actual members here (breaks SIP <4.19)
+      QgsCoordinateTransformContext coordinateTransformContext;
     };
 
     QgsDataProvider( const QString &uri = QString(), const QgsDataProvider::ProviderOptions &options = QgsDataProvider::ProviderOptions() );

src/core/qgsdataprovider.h

@@ -24,6 +24,7 @@
 
 //#include "qgsdataitem.h"
 #include "qgsdatasourceuri.h"
+#include "qgscoordinatetransformcontext.h"
 #include "qgslayermetadata.h"
 #include "qgserror.h"
 
@@ -94,7 +95,7 @@ class CORE_EXPORT QgsDataProvider : public QObject
      */
     struct ProviderOptions
     {
-      int unused; //!< @todo remove me once there are actual members here (breaks SIP <4.19)
+      QgsCoordinateTransformContext coordinateTransformContext;
     };
 
     /**