Add trips

db/migrate/20230509094041_create_post_trips.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+ROM::SQL.migration do
+  change do
+    create_table :post_trips do
+      foreign_key :post_id, :posts, null: false
+      foreign_key :trip_id, :trips, null: false
+    end
+  end
+end