Add flipper gem and database migration/tables

db/migrate/20230523120753_create_flipper_tables.rb

@@ -0,0 +1,22 @@
+class CreateFlipperTables < ActiveRecord::Migration[7.0]
+  def self.up
+    create_table :flipper_features do |t|
+      t.string :key, null: false
+      t.timestamps null: false
+    end
+    add_index :flipper_features, :key, unique: true
+
+    create_table :flipper_gates do |t|
+      t.string :feature_key, null: false
+      t.string :key, null: false
+      t.string :value
+      t.timestamps null: false
+    end
+    add_index :flipper_gates, [:feature_key, :key, :value], unique: true
+  end
+
+  def self.down
+    drop_table :flipper_gates
+    drop_table :flipper_features
+  end
+end