ZEVA2 - user notifications

**Describe the task**
In zeva1, we have (1) a notification table, (b) a user_profile table, and a notification_subscription table that acts as a product table between (a) and (b). I think we can simplify this a bit in zeva2 by having the notifications as an enum, and by having a notifications scalar list column (https://www.prisma.io/docs/orm/prisma-client/special-fields-and-types/working-with-scalar-lists-arrays) in the users table (similar to how we have a `roles Role[]` column in the user table).

**Purpose**
This will allow users to subscribe/unsubscribe from notifications, and for us to send them notifications based on their subscriptions.

**Acceptance Criteria**
- [ ] Review the notification table and create an prisma enum based on the table (may not need all the original records; please use your best judgement!)
- [ ] Modify the users model to include a notifications column based on the enum mentioned above.
- [ ] Bring over the old notification subscriptions by updating the seed.ts file.