Rails 8 support

[HLFH]

• Version: git, master branch

Could not find compatible versions

Because every version of devise_token_auth depends on rails >= 4.2.0, < 7.3
  and rails >= 4.2.0, < 7.3 could not be found in https://github.com/rails/rails.git (at main@429f400),
  devise_token_auth cannot be used.
So, because Gemfile depends on devise_token_auth >= 0,
  version solving has failed.