improves postgres example

- enables track_commit_timestamp to support Watch API
- remove mentions of now deprecated dashboard
- use postgres:15 as minimum requirement
- add zed example call
- remove http from grpc address, caused confusion to users

datastores/postgres.yml

@@ -8,14 +8,16 @@
 #
 # SpiceDB settings:
 # pre-shared key: foobar
-# dashboard address: http://localhost:8080
 # metrics address: http://localhost:9090
-# grpc address: http://localhost:50051
+# grpc address: localhost:50051
 #
 # Postgres settings:
 # user: postgres
 # password: secret
 # port: 5432
+#
+# example call with zed:
+# zed schema read --endpoint=localhost:50051 --insecure=true
 
 version: "3"
 
@@ -46,9 +48,18 @@ services:
  - "database"
 
  database:
- image: "postgres"
+ image: "postgres:15"
  ports:
  - "5432:5432"
  environment:
  - "POSTGRES_PASSWORD=secret"
  - "POSTGRES_DB=spicedb"
+
+ init_database:
+ image: "postgres:15"
+ restart: "on-failure:3"
+ command: "psql -h database -U postgres -c \"ALTER SYSTEM SET track_commit_timestamp = on;\""
+ environment:
+ - "PGPASSWORD=secret"
+ depends_on:
+ - "database"