Webhook checks for device mount permissions

[bindsi]

adding checks for the new device mount permissions #726 in the Webhook so we can validate that these perms are valid before the configuration is applied

[bindsi]

Hey @kate-goldenring,
in the review comment #737 (comment) you suggested to implement the check in the webhook.
Where does the check have to be implemented? As far as I see from the implementation of the webhook, the configuration admissionRequest contains the new configuration and it is checked in validate_configuration whether the new configuration can be serialized into the configuration object. Since this object includes the DiscoveryHandlerInfo that has the flat discovery_details as a string, it cannot fail in the current implementation/check (if it is a string).
Do you suggest to add extra webhook check´s to parse into strong types (here UdevDiscoveryDetails) which might blow up the code?
Wdyt?

[kate-goldenring]

@bindsi, that is what i was thinking, parsing the discovery_details in the webhook to get an early catch. This obviously expands beyond this specific motivation but would be a nice to have.