♻️(yhub) create dedicated file for environment variables in development

For now the environment variable for yhub were added to the common file.
This number of environment is growing and is specific to yhub so we
decided to create a dedicated file for yhub

compose.yml

@@ -239,18 +239,11 @@ services:
     image: impress:yhub-development
     environment:
       HOME: /tmp # same reason as node-based services above (unmapped uid)
-      PORT: 3002
-      REDIS: redis://yhub-valkey:6379
-      POSTGRES: postgres://yhub:pass@yhub-postgres:5432/yhub
-      REDIS_PREFIX: yhub
-      # seed rooms from the legacy Django/S3 document store on first access —
-      # S3 endpoint/credentials come from env.d/development/common
-      SOFT_MIGRATION: "true"
-      # signs the calls made to the backend, which holds the public half
-      YHUB_JWT_PRIVATE_KEY_FILE: /data/jwt/yhub-private.pem
+    # its own file rather than the backend's: this server reads none of the
+    # django settings `common` carries, and everything it does read is in there
     env_file:
-      - env.d/development/common
-      - env.d/development/common.local
+      - env.d/development/yhub
+      - env.d/development/yhub.local
     volumes:
       - ./data/jwt:/data/jwt:ro
       # editing a source file restarts the server (nodemon), no rebuild