[SRU] Backport to 22.04 LTS

[Gabriel Nagy]

As part of our entreprise desktop offering, there is the request to backport ubuntu-proxy-manager to 22.04 LTS. The package is in universe for now.

Ubuntu Proxy Manager is a D-Bus mediated service intended to be triggered by ADSys, our Active Directory GPO integration. ADSys has been available starting Ubuntu 21.04, and Ubuntu Proxy Manager was first released in Ubuntu 23.04.

It depends on the new golang 1.22 SRU attached to https://bugs.launchpad.net/ubuntu/+source/golang-1.22/+bug/2059756

[Impact]

 * ubuntu-proxy-manager is a new package. Impact is thus only for people installing.
 * To leverage the functionality of the package, a recent enough ADSys version must be used (at least 0.11.0, not currently in Jammy but there are approved plans to backport ADSys 0.13.2).
 * In addition to the ADSys requirement above, the machine must be Pro-enabled and a Proxy GPO must be configured on the Windows AD controller.
 * No impact is expected if the conditions above are not met.
 * This is a entreprise feature requested by desktop customers running LTS.

[Test Plan]

 1. Configure your machine with AD, with a correctly configured SSSD and KRB5 (AD user should be able to log in). Instructions can be found on https://github.com/ubuntu/adsys/wiki/2.-Prerequisites
 2. Install admx and adml files on your AD controller: https://canonical-adsys.readthedocs-hosted.com/en/stable/how-to/set-up-ad/
 3. Join machine to Ubuntu Pro to enable proxy policy application
 4. Configure some proxy settings in AD (https://canonical-adsys.readthedocs-hosted.com/en/stable/explanation/proxy/), for instance:
  * HTTP Proxy
  * Ignored hosts
 5. Install ADSys (at least version 0.11.0) and ubuntu-proxy-manager, then run `adsysctl update -m` to force a refresh of the policies
 6. Ensure GSettings/APT/environment proxy values are correctly set (full list of supported proxy backends can be seen here: https://github.com/ubuntu/ubuntu-proxy-manager#supported-backends)
 7. Remove/purge the ubuntu-proxy-manager package and run `adsysctl update -m` again -- a warning should show reflecting that ADSys has detected a configured proxy policy but ubuntu-proxy-manager is not installed for it to be applied. ADSys's exit code will remain 0.

[Where problems could occur]

 * Network access of various programs will be hindered if incorrect proxy settings are configured.

[Other Info]

 * The current version of ADSys in Jammy does not interact with this package whatsoever, but there are plans to backport the latest version.
 * A passing PPA build for ubuntu-proxy-manager can be seen here: https://launchpad.net/~gabuscus/+archive/ubuntu/ppa/+sourcepub/15678628/+listing-archive-extra
 * We have previously requested a FFe for ubuntu-proxy-manager for Focal: https://bugs.launchpad.net/ubuntu/jammy/+source/adsys/+bug/2012371

[Gabriel Nagy (gabuscus)]

ubuntu-proxy-manager (new package) is uploaded and currently in the NEW queue https://launchpad.net/ubuntu/jammy/+queue?queue_state=0&queue_text=ubuntu-proxy-manager