Mntor 1539/separate data ingestion (#3034)

MNTOR-1539 - create Google Cloud Function version of /hibp/notify API endpoint

Author: rhelmer

README.md

@@ -88,6 +88,30 @@ We track commits that are largely style/formatting via `.git-blame-ignore-revs`.
 
 2. You may receive the error `Required environment variable was not set`.  If this is the case, get the required env var(s) from another team member or ask in #fx-monitor-engineering.  Otherwise, if the server started successfully, navigate to [localhost:6060](http://localhost:6060/)
 
+### Cloud Functions
+
+User breach notifications from HIBP are handled by a [GCP Cloud Function](https://cloud.google.com/functions). This can be emulated locally:
+
+```sh
+npm run functions
+```
+
+This function serves the `/api/v1/hibp/notify` route, which is responsible for:
+
+1. receiving HTTP POST payloads with a bearer token from HIBP
+2. emailing any affected users
+
+This can be tested using curl:
+
+```sh
+curl \
+  -H 'Content-Type: application/json' \
+  -H 'Authorization: Bearer unsafe-default-token-for-dev' \
+  -X POST \
+  -d '{"breachName": "Gravatar", "hashPrefix": "...", "hashSuffixes": ["..."]}' \
+  localhost:8080/api/v1/hibp/notify
+```
+
 ### Database
 
 To create the database tables ...