Creation of PfsConfig files for SuNSS/DCB data

Currently we are using the 0xdeadbeef PfsConfig file for SuNSS data. This will need to change once we take into account the SuNSS rotator. Please provide a scheme taking this into account.

Quoting from a comment from rhl in DAMD-91, which still needs to be followed up:

With the current proposal to drive SuNSS to the appropriate hardstop at the beginning of each exposure (or possibly pointing) the rotator angle will not be known until we start observing. I think that this can be handled by having a standard pfsDesign for SuNSS which is converted to pfsConfig once the angle is known. Ideally this only matters for SuNSS's imaging leg, but that depends on the uniformity of the diffused illumination. This relies on knowing the position angle sufficiently accurately which is not, I think, a problem. If we need a better measurement I suspect that we can get it from a short n channel integration summed in the wavelength direction.

There is one major difference from regular PFS operations, namely that we cannot specify the fiberId in the pfsDesign file because we don't control the rotator angle. I think this is OK; we'd set it to -1 (a number which will have to go into the datamodel; real IDs start at 1 so 0 would be an option, but -1 seems safer to me as it's obviously invalid) and the real fiberId would be written by the code that writes the pfsConfig. Who owns the code that does this transformation? I assume that it's usually done as part of cobra configuration.