Fixes #35088 - Remove GCE Compute resource code

All code related to GCE compute resource
is now in Foreman Google plugin

https://github.com/theforeman/foreman_google

Fixes #35626 - Registration & proxy's registration_url

Use registration_url from Registration SP module
for registration command.

RFC: https://community.theforeman.org/t/rfc-host-registration-and-load-balancers/30462
Katello: https://projects.theforeman.org/issues/35627...

Fixes #35359 - Add cacert to http proxy (#9348)

This PR adds a cacert column to the http proxy and uses to this for
connecting to ec2 and other compute resources. This would also be used
by katello/other plugins when communicating to the CDN over a https...

Fixes #34526 - Switch Rails version to 6.1

Changes overview:
- Set default Rails version to 6.1
- Required dynfow >= 1.6.5
- Cleanup deprecation warnings in config/as_deprecation_whitelist.yaml
- ActiveSupport::ParameterFilter instead of ActionDispatch::Http::ParameterFilter...

Fixes #34913 - Take plugins into consideration when checking pending migrations

Also unify migration pending checking

Fixes #30122 - remove usage of controller level force_ssl

Foreman's use case for HTTP-only is provisioning. Many installers, like Red
Hat's Anaconda or Debian Preseed, either do not support it or make it very hard
to use HTTPS. This is especially hard since often a custom CA is used so the...

Fixes #34234 - do not allow HTTP on SmartProxy Auth

SmartProxyAuth enabled on its endpoints HTTP to log a message, that ssl is required.
This in not necessary and it is hard to keep for the future as Rails 6.1 will make that harder.

There is not too much benefit from this, so it's better to drop it.

Fixes #34236 - Drop require_ssl_smart_proxies setting

This defaults to true and setting it to false can create security
problems. Mandating client SSL certificates creates a more secure
environment.

Previously when require_ssl_smart_proxies was false, reverse DNS was...

Fixes #33697 - Registration - smart proxy features

Registration through smart proxy works only if proxy
have enabled 'Templates' and 'Registration features'.

This fix proxy selection in UI form and generating command via API.

Fixes #32678 - katello_ca_consumer in registration template

Move `rhsm_reconfigure` script from `katello_consumer.rpm` to
`global_registration` template so the `rpm` is not needed anymore

Migrated script is without support of RHEL5 and older
`subscription-manager` versions (0.96 and bellow)