Add Stripe Payment support

Add new Payment UI. This allows for payment of deposit or full (or some other amount) for the logged in member, as well as an optional other amount. It also allows for the addition of a payment for other members. Finally, the payment page handles all of the required Stripe payment inputs and submission. Upon success, there's a redirect to a success page.
- The backend handles creation of the payment intent as well as providing a webhook to respond to the payment result.
Registering for the convention creates a debit in the transaction table for the membership cost.
update membership email with payment url and new payment address
added a transaction table storing debts and payments. Debts come from buying memberships, payments can come via an admin creating a record (say to record a cheque), or from a stripe payment.
- Note that we allow a single payment to pay for multiple memberships (or deposits). As such a single stripe transaction can result in multiple new payment transactions being created. The underlying stripe Charge record (that generated these separate transactions), gets recorded in the new stripe table.
Added a new UI for the transactions. Admin only at this stage.
Add an AmountOwed component to the header, making it clear how much a person owes us. It's a button linking to the payment page.
Refactored the Membership code to share more code from packages/amber. Much of it is identical, so only those bits that differ are split off.
refactor most apis to use shared code where possible. With the shared api code living in packages/api. This actually accounts for a lot of the file changes.
standardized on a single parameterized hook to invalidate queries, then exposed a number of specific variants based on sets of queries. (this sadly caused a lot of changes)
moved the graphql source into the database package. This alls me to continue to generate the client bindings as well as a more bare set of types and documents for use on the backend.
Update Covid policy

new required environment variables are:

STRIPE_PUBLISHABLE_KEY STRIPE_SECRET_KEY STRIPE_WEBHOOK_SECRET

Note that the payment code is not hooked up to acus yet. Shouldn't be hard, but ran out of time

Name	Status	Preview	Updated (UTC)
amber-acus	✅ Ready (Inspect)	Visit Preview	Jun 7, 2023 3:58pm
amberconnw	✅ Ready (Inspect)	Visit Preview	Jun 7, 2023 3:58pm

ggascoigne / amber

Add Stripe Payment support #126