Add E2EE API (#13820)

db/migrate/20200518083523_create_encrypted_messages.rb

@@ -0,0 +1,15 @@
+class CreateEncryptedMessages < ActiveRecord::Migration[5.2]
+  def change
+    create_table :encrypted_messages do |t|
+      t.references :device, foreign_key: { on_delete: :cascade }
+      t.references :from_account, foreign_key: { to_table: :accounts, on_delete: :cascade }
+      t.string :from_device_id, default: '', null: false
+      t.integer :type, default: 0, null: false
+      t.text :body, default: '', null: false
+      t.text :digest, default: '', null: false
+      t.text :message_franking, default: '', null: false
+
+      t.timestamps
+    end
+  end
+end