Handling missing metadata
Some tables' metadata do not respect the SDMX structure. Should the code be robust against these issues, or do we rely on the database fixing the issue?
Ex1: Table doesn't have Constraint: http://api.data.abs.gov.au/dataflow/ABS/ABS_CENSUS2011_B24_LGA/1.0.0?references=all&detail=referencepartial
Ex2: No CubeRegion in Constraint/ContentConstraint (type = 'actual'), as needed for get_constraints: http://nsi-demo-oecd-staging.siscc.org/rest/dataflow/OECD.SDD/NAMAIN_T0107_A/1.0?references=all&detail=referencepartial