added schemes migration

db/migrate/20220608144156_create_schemes.rb

@@ -0,0 +1,11 @@
+class CreateSchemes < ActiveRecord::Migration[7.0]
+  def change
+    create_table :schemes do |t|
+      t.string :code
+      t.string :service
+      t.references :organisation, null: false, foreign_key: true
+
+      t.timestamps
+    end
+  end
+end