refs https://github.com/TryGhost/Team/issues/2078
The check for creating free Tiers needs to be explicit, rather than implicit
because the type is optional, we only want to error if it is explicitly passed
as "free", not if it is missing as "paid".
refs https://github.com/TryGhost/Team/issues/2078
Having to map between snake_case and camelCase was becoming confusing, so this
updates the Tier object to exclusively use camelCase, and the snake_case for the
API can be handled by the serializer/mapper or at the controller level.
refs https://github.com/TryGhost/Team/issues/2078
This removes the burden from the Tier object, and allows us to reuse
the existing slug generation implementation we have in our bookshelf
models.
refs https://github.com/TryGhost/Team/issues/2078
This pulls the current Tiers logic into its own package, the persistence part of
the work has not been done yet, that will be handled in core, so all bookshelf
model specific stuff is kept together.
