feat: Add Platform APIs (#1456)

db/migrate/20201123195011_create_platform_apps.rb

@@ -0,0 +1,8 @@
+class CreatePlatformApps < ActiveRecord::Migration[6.0]
+  def change
+    create_table :platform_apps do |t|
+      t.string :name, null: false
+      t.timestamps
+    end
+  end
+end

db/migrate/20201124101124_create_platform_app_permissibles.rb

@@ -0,0 +1,11 @@
+class CreatePlatformAppPermissibles < ActiveRecord::Migration[6.0]
+  def change
+    create_table :platform_app_permissibles do |t|
+      t.references :platform_app, index: true, null: false
+      t.references :permissible, null: false, polymorphic: true, index: { name: :index_platform_app_permissibles_on_permissibles }
+      t.timestamps
+    end
+
+    add_index :platform_app_permissibles, [:platform_app_id, :permissible_id, :permissible_type], unique: true, name: 'unique_permissibles_index'
+  end
+end