Use `xds_from_ms(...,table_where)` to select the FIELD_ID

[SpheMakh]

The call
https://github.com/laduma-dev/contsub/blob/54dc019bfc1aca207bd36908159bcf2fa91440d1/contsub/utils.py#L250-L255

should be

 ms_dsl = xds_from_ms( 
     ms_path,  
     index_cols=["TIME", "ANTENNA1", "ANTENNA2"],
     group_cols=["DATA_DESC_ID"],
     taql_where="FIELD_ID=={field_id}"
     chunks={"row": chunks }  
 )

• It may also be worth considering multiple spectral window's. Otherwise, it doesn't make sense to query all of them and then only use one.
• Also need to check if resulting xr.Dataset has a FIELD_ID attribute to make sure the data written correctly later on.