Cannot use the `append_content_security_policy_directives` method in `ApplicationController`

The append_content_security_policy_directives from SecureHeaders can be referenced in ApplicationController as follows:

class ApplicationController < ActionController::Base
  def foo
    append_content_security_policy_directives(xxxx)
  end
end

However, Sorbet seems unable to find append_content_security_policy_directives.

Method append_content_security_policy_directives does not exist on ApplicationController

By the way, the method is generated in RBI as follows:

# sorbet/rbi/gems/secure_headers@7.1.0.rbi
module SecureHeaders
  def append_content_security_policy_directives(additions); end
  # ...
end

Therefore, it's possible that ActionController and SecureHeaders are not linked correctly.

Start by reviewing the generated sorbet/rbi/gems/secure_headers@7.1.0.rbi and the ApplicationController usage described in the issue. Trace how SecureHeaders is included or extended in ActionController and how Tapioca links those declarations. Done means Sorbet recognizes append_content_security_policy_directives when called from ApplicationController, with coverage for the reported setup.