refs https://github.com/TryGhost/Team/issues/1163
We want to make the title for Offers optional, our nullable validation
means that we cannot store an empty string, so we must remove the NOT
NULL constraint from the column if we want to store either an empty
value or null.
There is a bug with editing columns in SQLite with `knex` which strips all
the indexes, so we have to manually add them afterwards.
no-issue
* Removed NOT_NULL constraint from stripe_coupon_id
When handling disconnecting from Stripe - we remove all Stripe data from
our database to ensure we do not have bad/invalid data stored. Removing
this constraint will allow us to set the value to NULL.
* Added created_at column to offer_redemptions
Offer Redemptions are not just a joining table, but an event. A created_at
date allows them to be ordered
Because this is in alpha it is simpler to just drop the tables and
re-add them, due to offer_redemptions depending on offers, we also drop
this table and re-add it.
