Create API webhook, endpoints for subscription payments using Stripe

- Add fields to mark users as subscribed to a specific plan and
  subscription renewal date in DB
- Add ability to unsubscribe a user using their email address
- Expose webhook for stripe to callback confirming payment

pyproject.toml

@@ -73,7 +73,8 @@ dependencies = [
     "gunicorn == 21.2.0",
     "lxml == 4.9.3",
     "tzdata == 2023.3",
-    "rapidocr-onnxruntime == 1.3.8"
+    "rapidocr-onnxruntime == 1.3.8",
+    "stripe == 7.3.0",
 ]
 dynamic = ["version"]