- These initializers are new defaults for Rails 5 and newly generated
  apps do not need to change them.
- Fixes #25181

- Fixes #25180

View files is necessary to send mail, it should be generated even Rails API.
Fixes #23617

Test of Rails API should be in `api_app_generator_test.rb`.

Because the form is not in the Rails API,
`per_form_csrf_tokens` initializer I think unnecessary.

We will wait until 5.1 to make a decision

We don't need to set config.debug_exception_response_format given that :api is the default value for only API apps

behavior

In rails api, since default is so as not to use the `protect_from_forgery`,
`request_forgery_protection` initializer I think that's unnecessary