♻️(yhub) maintain database schema using npm run init-db

The yhub database schema have new update and will probably be modified
in the future. We don't want to maintain this sql schema in the Docs
repo, we want to reuse what is directly made in the yhub project. For
this we reuse the existing bin/init-db.js script

src/yhub-server/README.md

@@ -52,6 +52,25 @@ backend-internal and should not be routed through the public ingress.
 The `Dockerfile` builds the container image used by the `yhub` service in
 `compose.yml`.
 
+## Database schema (`npm run init-db`)
+
+yhub never runs DDL from the server or the worker, so the schema is created by
+the script it ships (`node_modules/@y/hub/bin/init-db.js`), wrapped here as
+`npm run init-db`. It reads `POSTGRES` from the environment, creates the
+database when it does not exist, then every table and index the **installed**
+yhub version needs. It is idempotent, so re-running it is always safe.
+
+Run it whenever `@y/hub` is upgraded — releases that add a table or a column
+say so in their changelog, and the server fails on every document read until
+the DDL is applied (`relation "yhub_ydoc_tombstones_v1" does not exist`, for
+instance). Nothing in this repository copies the schema, so an upgrade is
+`package.json` plus this script and nothing else.
+
+From the repository root, `make migrate-yhub` runs it against the dev stack —
+the counterpart of `make migrate` for the Django database. `make bootstrap`
+already includes it, so a fresh checkout needs nothing extra; an upgrade is
+`make migrate-yhub` and restart the service.
+
 ## Soft migration (`SOFT_MIGRATION=true`)
 
 Documents were historically stored by the Django backend in the S3 media

src/yhub-server/package.json

@@ -3,7 +3,8 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "start": "node server.js"
+    "start": "node server.js",
+    "init-db": "node node_modules/@y/hub/bin/init-db.js"
   },
   "dependencies": {
     "@y/hub": "0.6.0",