Update the README

web/apps/payments/README.md

@@ -1,6 +1,92 @@
 Code that runs on `payments.ente.io`. It brokers between our services and
 Stripe's API for payments.
 
+## Development / New
+
+There are three pieces that need to be connected to have a working local setup:
+
+- A client app
+- This web app
+- Museum
+
+### Client app
+
+For the client, let us consider the Photos web app (similar configuration can be
+done in the mobile client too).
+
+Add the following to `web/apps/photos/.env.local`:
+
+```env
+NEXT_PUBLIC_ENTE_ENDPOINT = http://localhost:8080
+NEXT_PUBLIC_ENTE_PAYMENTS_ENDPOINT = http://localhost:3001
+```
+Then start it locally
+
+```sh
+yarn dev:photos
+```
+
+This tells it to connect to the museum and payments app running on localhost.
+
+> For connecting from the mobile app, you'll need to run museum on a local IP
+> instead localhost. If so, just replace "http://localhost:8080" with (say)
+> "http://192.168.1.2:8080" wherever mentioned.
+
+### Payments app
+
+For this (payments) web app, configure it to connect to the local museum, and
+use a set of (development) Stripe keys which can be found in [Stripe's developer
+dashboard](https://dashboard.stripe.com).
+
+Add the following to
+`web/apps/payments/.env.local`
+
+```env
+NEXT_PUBLIC_ENTE_ENDPOINT = http://localhost:8080
+NEXT_PUBLIC_STRIPE_US_PUBLISHABLE_KEY = stripe_publishable_key
+```
+
+Then start it locally
+
+```sh
+yarn dev:payments
+```
+
+### Museum
+
+1. Install the [stripe-cli](https://docs.stripe.com/stripe-cli) and capture the
+   webhook signing secret.
+
+2. Define this secret within your `musuem.yaml`
+
+3. Update the `whitelisted-redirect-urls` so that it supports redirecting to
+   the locally running payments app.
+
+Assuming that your local payments app is running on `localhost:3001`, your
+`server/museum.yaml` should look as follows.
+
+```yaml
+stripe:
+    us:
+        key: stripe_dev_key
+        webhook-secret: stripe_dev_webhook_secret
+    whitelisted-redirect-urls: ["http://localhost:3001/gallery", "http://192.168.1.2:3001/frameRedirect"]
+    path:
+        success: ?status=success&session_id={CHECKOUT_SESSION_ID}
+        cancel: ?status=fail&reason=canceled
+```
+
+Finally, start museum, for example:
+
+```
+docker compose up
+```
+
+Now if you try to purchase a plan from your locally running photos web client,
+it should redirect to the locally running payments app, and from there to
+Stripe. Once the test purchase completes it should redirect back to the local
+web client.
+
 ## Development
 
 If you're running this to test out the payment flows end-to-end, please do a