fixes #17395 - use admin user for load_template_vars

When `load_template_vars` is called from before_action, the current user
must already be set to ensure caching of parameters inside Host#params
is done with consistent permissions. Otherwise when Foreman::Renderer's...

Fixes #12156 - Adds email configuration into Foreman settings

Instead using email.yaml, the email configuration
can be modified dynamically via settings.
(cherry picked from commit 5a8f4579cbf581b7c54d86f3dc055d45362e6508)

Fixes #17487 - support sessions for api calls

- authenticated api calls save user to session and set
flag api_authenticated_session
- sessions with such flag allow posting requests without CSRF token
- api sessions exipre the same way as UI sessions
- api sessions don't store any additional data to keep the requests...

Fixes #16422 - Foreman API throws ruby exception with ovirt network API

Passing a 'nil' resource_class to the `scope_for` method will always result in a 500 as you cannot call `.where` on nil.
(cherry picked from commit 9fb9397a7c8cbd96151cec54f2c4718f1a56ee96)

fixes #11127 - show error when rebuild reboot fails

(cherry picked from commit 6695a5563dc244522c7eb2135b8ab827f1d80411)

Fixes #17296 - Add setting access_unattended_without_build

(cherry picked from commit 2652deaf8f81cf315eed8f61b675a73bce0c6eff)

Fixes #17343 - set deep munge config off

deep_munge was introduced as a solution to keep
Rails secure by default which results in
'empty array becomes nil in params'.
Thats why, set deep_munge config off in application.rb.
Also, added changes which will cast param argument to string...

Fixes #17441 - override all parameters permission changed to edit

Fixes #16739 - unify parameters permissions

Fixes #17403 - enable exporting of templates