Fixes #21450 - Update rubocop to 0.51.0

Fixes #21026 - Clear cached notifications properly

Using `delete_all` for has_many does not trigger callbacks
on the associated objects, `dependent: :destroy` does.

Clearing the cache needs to happen anytime a notification
gets created, modified and destroyed, `after_commit`...

fixes #21394 - user login with access token api

Fixes #21119 - set taxonomies in API

With this we correctly set the default taxonomy for non-admin users
in API calls. Admins are not touched at all, their context remains
"any context" for API calls. This also refactors various places
where tried to set the right taxonomy and combines them into single...

Fixes #18736 - Forced unlimited check for filter with no t (#4724)

Fixes #21175 - Unable to add AD LDAP Auth Source

Fixes #21037 - use Host::Base as auditable_type

Otherwise, we are hitting "Invalid single-table inheritance type:
Host::Discovered is not a subclass of Host::Managed" when converting the
host from discovered to managed.

Fixes #15409 - Separated puppet facts from core

Fixes #20201 - Global HTTP proxy for outgoing requests

This introduce two new settings to proxy outgoing HTTP
requests and one to except certain hosts from it.

The extensions for Excon::Connection and Net::HTTP
allow setting a proxy on their requests.

Fixes #20958 - Don't pass argument to force association reload