Non-kwargs requests are deprecated now.
Guides are updated as well.
`post url, nil, nil, { a: 'b' }` doesn't make sense.
`post url, params: { y: x }, session: { a: 'b' }` would be an explicit way to do the same
When the value for the required key is empty an ActionController::ParameterMissing is raised which gets caught by ActionController::Base and turned into a 400 Bad Request reply with a message in the body saying the key is missing, which is misleading.
With these changes, ActionController::EmptyParameter will be raised which ActionController::Base will catch and turn into a 400 Bad Request reply with a message in the body saying the key value is empty.
