Add method DerivedProjectedCRS::demoteTo2D and implement promoteTo3D

[jjimenezshaw]

DerivedProjectedCRS do not work properly with promoteTo3D and demoteTo2D.
This PR tries to implement that functionality.

• Tests added
• Added clear title that can be used to generate release notes

[rouault]

Looks good to me. You just have to add the new symbol in scripts/reference_exported_symbols.txt as suggested below (you can also manually insert it from the suggestion of the diff if not running Linux)

 --- /tmp/reference_exported_symbols.txt	2022-09-11 10:16:28.063469486 +0000
+++ /tmp/got_symbols.txt	2022-09-11 10:16:28.091469784 +0000
@@ -169,6 +169,7 @@
 osgeo::proj::crs::DerivedGeographicCRS::~DerivedGeographicCRS()
 osgeo::proj::crs::DerivedProjectedCRS::baseCRS() const
 osgeo::proj::crs::DerivedProjectedCRS::create(osgeo::proj::util::PropertyMap const&, dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::crs::ProjectedCRS> > const&, dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::operation::Conversion> > const&, dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::cs::CoordinateSystem> > const&)
+osgeo::proj::crs::DerivedProjectedCRS::demoteTo2D(std::string const&, std::shared_ptr<osgeo::proj::io::DatabaseContext> const&) const
 osgeo::proj::crs::DerivedProjectedCRS::~DerivedProjectedCRS()
 osgeo::proj::crs::DerivedVerticalCRS::baseCRS() const
 osgeo::proj::crs::DerivedVerticalCRS::create(osgeo::proj::util::PropertyMap const&, dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::crs::VerticalCRS> > const&, dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::operation::Conversion> > const&, dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::cs::VerticalCS> > const&)
Difference(s) found in exported symbols. If intended, refresh scripts/reference_exported_symbols.txt with 'scripts/dump_exported_symbols.sh lib/libproj.so > scripts/reference_exported_symbols.txt'

[jjimenezshaw]

Looks good to me. You just have to add the new symbol in scripts/reference_exported_symbols.txt as suggested below (you can also manually insert it from the suggestion of the diff if not running Linux)

Thanks Even. I have just added that line.

Looks like I do not have to add anything to the *.rst documentation, right?

[rouault]

Looks like I do not have to add anything to the *.rst documentation, right?

no, nothing needed on the documentation side

You might also want to run the ./scripts/reformat_cpp.sh script to make sure the code is formatted consistently with the rest, but as you rightly adapted similar existing code, I suspect it should already be properly formatted (this isn't checked by CI, as this might be a bit painless for people with have not the right setup to run the formatter, so from time to time I run it on my side)

[jjimenezshaw]

Does it make sense to do the same (promoteTo3D and demoteTo2D) for EngineeringCRS? In that case, I can make a PR for that.

[rouault]

Does it make sense to do the same (promoteTo3D and demoteTo2D) for EngineeringCRS?

maybe... ? But I don't see a strong need to add that, at least now. PROJ cannot do much with EngineeringCRS apart import/export from/into WKT/PROJJSON, so I don't see a pressing need for adding those methods, whose main usefulness is for createOperations() purposes.