In order to:
- avoid confusion between having multiple
dbs: dataSources.db.* in resolvers and this.db.* in data source
- more closely match knex docs (which say eg
knex.select().from('users')), so we'd do
this.knex.select().from('users')
instead of
this.db.select().from('users')
https://github.com/cvburgess/SQLDataSource/blob/master/index.js#L17