add LoginErrorCode

packages/app/src/interfaces/errors/login-form-error.ts

@@ -0,0 +1,5 @@
+export const LoginErrorCode = {
+  PROVIDER_DUPLICATED_USERNAME_EXCEPTION: 'ProviderDuplicatedUsernameException',
+} as const;
+
+export type LoginErrorCode = typeof LoginErrorCode[keyof typeof LoginErrorCode];