Adds Subscription API

[ikreymer]

Fixes #1905

(Different approach than originally suggested, but accomplishes same ends for tracking subscription history in SaaS setup)

Adds a new top-level /api/subscriptions endpoint and SubOps handler on the backend.

The subscription api supports /api/subscriptions/create, /api/subscriptions/update and /api/subscriptions/cancel.

• /api/subscriptions/create creates a new org with subscription, extending the work done in Extends Org Create endpont + shared secret auth #1897. The original /api/orgs/create is reverted as before, while this endpoint can be used to create a new org with additional options.

• /api/subscriptions/update can be used to update subscription data, including status, readOnlyOnCancel and extra details (see below)

• /api/subscriptions/cancel can be used to cancel a subscription. By default, this will result in the org also be deleted, unless readOnlyOnCancel was previous set.

All subscription events are timestamped and also logged in the MongoDB subscription collection.

All operations can only be accessed via the shared secret auth added in #1897, or with superadmin login.

The Subscription optionally stored on the org in subscription is as follows:

class Subscription(BaseModel):
    """subscription data"""

    subId: str
    status: str
    planId: str

    futureCancelDate: Optional[datetime] = None
    readOnlyOnCancel: bool = False

The subId is used to uniquely identify subscriptions, and must be unique if set (via sparse unique index on the Org).
The planId field is used to identify an arbitrary plan for the subscription.
status and futureCancelDate can be used to display status and cancellation info for the user.
readOnlyOnCancel indicates where the whole Org should be deleted when a subscription is canceled via /api/subscriptions/cancel.

TODOs:

• new POST /subscriptions/create, /subscriptions/update, /subscriptions/cancel API endpoints
• Subscriptions mongo collection storing timestamped /subscription API events
• GET /subscriptions/events API to get subscription events
• Subscription data model
• Support for setting and handling readOnlyOnCancel on org
• /org/subscription info with external API call to get portalUrl
• subscription in org getter and list views
• subscription API endpoints available only if billing_enabled is set in helm chart
• Mark org as readOnly for subscription status paused_payment_failed, clears it on status active

[SuaYoo]

Some feedback based on API docs!

[SuaYoo]

Can this be any date time format, or UTC?

[ikreymer]

It should be datetime UTC, believe it will return an ISO string in UTC.