Add heroku-connect to Docker compose file

This commit adds the heroku-connect container as documented in:

https://github.com/RaspberryPiFoundation/heroku-connect

This means that building the project now requires authenticating with
`ghcr.io` by doing:

$ echo $GITHUB_TOKEN | docker login ghcr.io -u <github-username> \
   --password-stdin

Where $GITHUB_TOKEN is a PAT with `packages:read` permissions (same as
you use for NPM).

Author: fspeirs

docker-compose.yml

@@ -53,7 +53,29 @@ services:
     platform: linux/amd64
     command: -u $SMEE_TUNNEL -t http://api:3009/github_webhooks
 
+  salesforce_connect:
+    image: ghcr.io/raspberrypifoundation/heroku-connect
+    volumes:
+      - salesforce_connect_data:/var/lib/postgres/data/
+    environment:
+      - POSTGRES_DB=salesforce_development
+      - POSTGRES_CLONE_DB=salesforce_test
+      - POSTGRES_PASSWORD=password
+      - POSTGRES_USER=postgres
+    healthcheck:
+      test:
+        [
+          "CMD-SHELL",
+          "pg_isready -h 127.0.0.1 -U $${POSTGRES_USER} -d $${POSTGRES_DB}",
+        ]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+    ports:
+      - "4101:5432"
+
 volumes:
   postgres-data:
   bundle-data:
   node_modules:
+  salesforce_connect_data: