Run clang-tidy modernize-use-override to remove all the redundant
virtual keywords from overridden methods, and add some missing
overrides.
Another benefit is that this has also added the overrides
on destructors, which will cause a build failure if a base
class is missing a virtual destructor.
Sometimes it's necessary to manually call this, instead of
deleting the exporter and letting it be called automatically
There's a chance that features in the buffer will cause errors
while being exported, and if the only way to flush the buffer
is to delete the exporter then there's no way to detect or
retrieve these errors.
Flags can be used to control how features are added to the sink.
For now, there's only a single flag available - FastInsert.
When FastInsert is set, faster inserts will be use at the cost
of updating the passed features to reflect changes made at the
provider.
This includes skipping the update of the passed feature IDs
to match the resulting feature IDs for the feature within
the data provider.
Individual sink subclasses may or may not choose to respect
this flag, depending on whether or not skipping this update
represents a significant speed boost for the operation.
QgsVectorLayer always ignores the flag - feature ids are
required for the featureAdded signal to be correctly emitted,
and it's expected that performance critical applications will
add features directly to a data provider instead of
via QgsVectorLayer's edit buffer.
Since the majority of users of this class will be exporting
an existing map layer to a data provider, the QgsVectorLayerImport
name is misleading and suggests that this class is designed
just to bring layers "into" QGIS.
Explicitly naming the class "Exporter" should help API users
discover this class.
Also cleanup API and improve docs
