Shared column schema: espn mbb season groups schema

Columns shared verbatim across: espn_mbb_season_groups, espn_nba_season_groups.

Details

col_name	types	description
league	character	League slug.
season	integer	Season year.
season_type	integer	Season-type id.
group_id	character	ESPN group id.
ref	character	$ref URL for the group detail.