refs https://github.com/TryGhost/Team/issues/710
This allows us to fetch the default monthly and yearly price models for
a product model, which is important since we no longer want to expose
the entire list of prices, but just the designated monthly & yearly prices.
refs https://github.com/TryGhost/Team/issues/586
We have to use `belongsToMany` because of the way bookshelf relations
work. In reality the relationship is 'hasMany', e.g. a Product has many
Stripe Prices.
These relations are the minimal needed to satisfy the following
relationships without transforming the results. (e.g. flattening the
StripePrices from a list of StripeProducts for a Product)
Product -> StripeProduct: product.related('stripeProducts')
StripeProduct -> StripePrice: stripeProduct.related('stripePrices');
Product -> StripePrice: product.related('stripePrices');
StripePrice -> Product: stripePrice.related('stripeProduct.product');
refs https://github.com/TryGhost/Team/issues/586
- Member model now has `products` relation, sorted using `sort_order`, following convention from `labels`
- Product model has handling to set `slug` from name, following convention of Label model
- Updated filter plugin to handle filtering Member models by their `product` relations e.g. `product:[slug, slug]`
