rails: HostAuthorization: confusing error message when using multiple hostnames

Steps to reproduce

Calling the application with different values for HTTP_HOST and HTTP_X_FORWARDED_HOST while HostAuthorization is enabled (i.e. config.hosts is set/active) while at least HTTP_HOST is not present in config.hosts.

Expected behavior

Error message that displays the user that both hostnames are checked and need to be added to config.hosts.

Example:

Blocked hosts: HTTP_HOST, HTTP_X_FORWARDED_HOST
---------------------------------------------------------------------------------------------
To allow requests to HTTP_HOST, HTTP_X_FORWARDED_HOST, add the following to your environment configuration:
config.hosts << "HTTP_HOST"
config.hosts << "HTTP_X_FORWARDED_HOST"

Actual behavior

Output

Blocked host: HTTP_X_FORWARDED_HOST
---------------------------------------------------------------------------------------------
To allow requests to HTTP_X_FORWARDED_HOST, add the following to your environment configuration:
config.hosts << "HTTP_X_FORWARDED_HOST"

If you then add HTTP_X_FORWARDED_HOST to config.hosts the error message is still displayed (unchanged) if HTTP_HOST is missing.

System configuration

Rails version: 6.0.3.3 (should be present since introduction of HostAuthorization in v6.0.0.beta1)

Ruby version: any

I created a commit that changes / fixes that behavior (See here) in a forked repository. I can create a pull request if needed / wanted.

Edit: Fixed wrong header name in issue description