In this case we don't need to propagate cleanup
function. It simplifies the code.

gitlab-sshd: Acceptance test for the discover command

See merge request gitlab-org/gitlab-shell!457

With this, we can start to build confidence in making changes to
gitlab-sshd.

Refactors introspection of execution environment to rely on
per-connection state (`gitlab-shell`) or per request (`gitlab-sshd`)

Relates to https://gitlab.com/gitlab-org/gitlab-shell/-/issues/496

Previously when the gitlab-shell log was not writable, gitlab-shell
would attempt to fall back to the syslog to log an error. However,
if the syslog logger creation succeeded, gitlab-shell would panic
since `err` was `nil`.

Relates to https://gitlab.com/gitlab-org/gitlab-shell/-/issues/510

* Counter for how many times the max concurrent sessions limit was hit.
* Histogram for duration of each SSH connection.

https://gitlab.com/gitlab-org/gitlab-shell/-/issues/121

Signed-off-by: Ben Kochie <superq@gmail.com>

Add a basic monitoring endpoint to the sshd command.
* Listen on localhost port 9122 by default.
* Integrate build/version info.
* Update example config.

https://gitlab.com/gitlab-org/gitlab-shell/-/issues/121

Signed-off-by: Ben Kochie <superq@gmail.com>

Use "omitempty" to allow defaults in the config file to be correctly
passed. Without this, explicitly setting an empty default like an empty
string will not work. Needed in order to allow explicitly disabling some
settings.

Related to: https://gitlab.com/gitlab-org/gitlab-shell/-/issues/121

Signed-off-by: Ben Kochie <superq@gmail.com>