feat: Add published_at column to flows and adjust update flow status

packages/backend/src/db/migrations/20220817121241_add_published_at_column_to_flows.ts

@@ -0,0 +1,13 @@
+import { Knex } from 'knex';
+
+export async function up(knex: Knex): Promise<void> {
+  return knex.schema.table('flows', (table) => {
+    table.timestamp('published_at').nullable();
+  });
+}
+
+export async function down(knex: Knex): Promise<void> {
+  return knex.schema.table('flows', (table) => {
+    table.dropColumn('published_at');
+  });
+}