Adding SQL Connector db connection option to enable SQL Auth

.env.example

@@ -1,3 +1,4 @@
+DB_CONNECTION_MODE=direct
 DATABASE_URL=postgres://postgres:postgres@127.0.0.1:5432/postgres
 
 # `openssl rand -hex 32`
@@ -9,3 +10,10 @@ NEXT_PUBLIC_NEXTAUTH_URL=https://localhost:3001
 OAUTH_REDIRECT_URI=https://localhost:3001/callback
 OAUTH_CLIENT_ID=local-client
 OAUTH_CLIENT_SECRET=****
+
+# Cloud SQL Auth Proxy (Cloud Connector) — these are relevant if DB_CONNECTION_MODE=connector
+# CLOUD_SQL_CONNECTION_NAME=PROJECT:REGION:INSTANCE
+# DB_USER=your_db_user
+# DB_PASSWORD=****
+# DB_NAME=your_db_name
+# CLOUD_SQL_IP_TYPE=PRIVATE

apphosting.yaml

@@ -59,3 +59,32 @@ env:
     availability:
       - BUILD
       - RUNTIME
+
+  # Database connection mode: "connector" (Cloud SQL Connector) or "direct" (DATABASE_URL).
+  - variable: DB_CONNECTION_MODE
+    value: direct
+    availability:
+      - RUNTIME
+
+  # Cloud SQL Connector settings (only used when DB_CONNECTION_MODE=connector).
+  - variable: CLOUD_SQL_CONNECTION_NAME
+    value: f3data:us-central1:f3data
+    availability:
+      - RUNTIME
+  - variable: DB_USER
+    value: app_codex
+    availability:
+      - RUNTIME
+  - variable: DB_PASSWORD
+    secret: client-database-password
+    availability:
+      - RUNTIME
+  - variable: DB_NAME
+    value: f3_prod
+    availability:
+      - RUNTIME
+
+  - variable: CLOUD_SQL_IP_TYPE
+    value: PUBLIC
+    availability:
+      - RUNTIME