[Actions] There is no possibility to validate action connector secrets and config together.

[YulNaumenko]

On the Alerting framework level we can validate action connector secrets and config properties only separately.
This will lead to the complexity to validate some secrets params which depends on the config params. For example email connector:
if config.hasAuth: true
we should validate secrets.username !== null && secrets.password !== null
We have this validation only on the client side, but it is still possible to create email connector with hasAuth = true, but with no username/password.
We need to provide API ability to validate actions config and secrets together.

[pmuellr]

My initial thought on this, is to add a new optional validation function on the rule type, which takes secrets AND config, and is run if both secrets and config are themselves validated. We'd then add this optional validation function to the connectors that need it.

Aside: I was wondering if connector params come into play here, but I don't think so, since they're only available when the connector is executed, and the executor is passed all of config, secrets, and params - additional validation of the params against config/secrets can be done in the executor.

Another potential way of doing this is via "hooks" on our APIs, as described in allow connector types to provide feedback during create/update/delete calls #106724. The idea is the create and update hooks could do the additional validation when they are called, and then return an indication of the validation failure to prevent the create/update from occuring.