Component: monitoring, salt

Why this is needed:
To manage the customization of Alertmanager configuration in a single place (Salt) and then expose it through CLI and UI to the user, so he can edit configuration to add receivers of inhibition rules.

What should be done:
Develop a Salt module exposing methods to show and edit Alertmanager configuration.

Implementation proposal (strongly recommended):
We will use the already existing metalk8s-alertmanager-config
ConfigMap to store the Alertmanager configuration
customizations.

A Salt module will be developed to manipulate this object, so the logic
can be kept in only one place.

This module must provide necessary methods to show or edit the configuration
in 2 different ways:

• simple
• advanced

The simple mode will only display and allow to change some specific
configuration, such as the receivers or the inhibit rules, and in an as
simple as possible manner for the user.

The advanced mode will allow to change all the configuration points,
exposing the whole configuration as a plain YAML.

This module should also ensure that the passed configuration is valid.

Test plan: