Investigate how to model results for non-round-robin competitions

[SebDuff]

For example, English championship and Dutch eredivisie
https://pypi.org/project/football-data-api/

[dallinb]

Looking at both the English Championship and the Dutch Eredivisie, for each match there is a stage and the games a labelled as REGULAR_SEASON. This matches what we have for the other leagues we deal with that are 100% round-robin (e.g the English Premiership). Therefore we ensure that we check for the stage matching REGULAR_SEASON when searching for matches.