feat: setup attachment to the freight chat

apps/edr-freight-api/src/migrations/2320000000000-SupportChatAttachments.ts

@@ -0,0 +1,50 @@
+import { MigrationInterface, QueryRunner } from "typeorm";
+
+/**
+ * Let a support message carry files instead of text.
+ *
+ * No new table: chat attachments reuse the polymorphic `freight.files` record
+ * with `resource = 'support_message'` and `resource_id = <message id>`, the same
+ * way bookings/contracts/companies already store theirs.
+ *
+ * The only schema change is dropping NOT NULL from `support_messages.body`, so
+ * an attachment-only message can say "there is no text" rather than smuggling
+ * that fact through an empty string. DROP NOT NULL is a catalog-only change in
+ * Postgres — no table rewrite, no long lock — so this is safe on a live table.
+ *
+ * The partial index on (resource, resource_id) is what makes hydrating a page of
+ * messages one indexed lookup instead of a scan of every file row in the system.
+ */
+export class SupportChatAttachments2320000000000 implements MigrationInterface {
+  name = "SupportChatAttachments2320000000000";
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      ALTER TABLE freight.support_messages
+      ALTER COLUMN body DROP NOT NULL
+    `);
+
+    await queryRunner.query(`
+      CREATE INDEX IF NOT EXISTS "IDX_FILES_RESOURCE_LOOKUP"
+      ON freight.files (resource, resource_id)
+      WHERE deleted_at IS NULL
+    `);
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      DROP INDEX IF EXISTS freight."IDX_FILES_RESOURCE_LOOKUP"
+    `);
+
+    // Re-imposing NOT NULL would fail on any attachment-only message written
+    // while this migration was applied. Backfill those to '' first so the
+    // rollback is deterministic rather than dependent on production data.
+    await queryRunner.query(`
+      UPDATE freight.support_messages SET body = '' WHERE body IS NULL
+    `);
+    await queryRunner.query(`
+      ALTER TABLE freight.support_messages
+      ALTER COLUMN body SET NOT NULL
+    `);
+  }
+}