Provide WCS for DAMD-2 PFSD files

We need a WCS for each raw AG image HDU – the ones which go into the PFSD files. The MCS/PFSC WCS is pixel->pfi_mm; if that is acceptable perhaps the pfs.utils.coordinates routine can be adapted?

Or do we need/want to provide a pixel->sky WCS for the raw PFSD files? That does not seem right, unless we decide that the PFSD files should contain more than the AGCC outputs.