refs https://github.com/TryGhost/Team/issues/1083
Instead of Offers being hardcoded to the "once" duration this will allow
Admins to start creating offers of variable durations.
no-issue
This adds the concept of "Value Objects" to an Offers properties,
allowing us to move validation out and ensure that an Offer will only
ever have valid properties, without having to duplicate checks - or
leave them to the persistent layer. This means we can fail early, as
well as write unit tests for all of our validation.
refs https://github.com/TryGhost/Team/issues/1090
When creating a Stripe Checkout Session for an Offer - we need access to
the underlying Stripe Coupon. Exposing it here allows consumers of the
OfferRepository access.
refs https://github.com/TryGhost/Team/issues/1090
When creating checkout session we will need to be able to look up Offers
from the OfferRepository. This exposes the repository so that it can be
passed as a dependency elsewhere.
