Add method to infer minimum compatible SSSOM version.

[gouttegd]

This PR adds a new method to the MappingSetDataFrame class to automatically determine the minimum version of the SSSOM specification the set is compatible with – that is, the earliest version that defines all the slots and all the enum values present in the set.

This method could later be used to implement the behaviour recommended by the spec: automatically inserting the sssom_version slot when a set is written, if the set requires another version than 1.0. This could simply look like:

# Assuming msdf is the mapping set we have to write
min_version = msdf.get_compatible_version()
if min_version != "1.0":
    msdf.metadata["sssom_version"] = min_version
# Now we can actually write the msdf

[gouttegd]

⚠️ This cannot work for now because the latest released version of sssom is still the 1.0.0 from last year, in which the sssom_version_enum does not exist.

[matentzn]

I just want to say a huge THANK YOU for these PRs.. Much appreciated.

I dont see any red flags, lgtm!

[gouttegd]

Marking as draft to prevent inadvertent premature merging.