[FEATURE] Provide the ability to configure TLS server certificate verification on webhook endpoints

[fawcettm91]

Is your feature request related to a problem?

Currently when connecting to a webhook endpoint, TLS server certificate verification is always performed meaning that the server name has to match and the cert has to be signed by a well known CA. Connections to any target endpoint that is using a custom CA will be rejected. It is currently not possible to skip TLS verification or provide custom certs to be used.

What solution would you like?

The ability to be able to specify that TLS verification should not be performed, as well as the ability to provide a custom CA to verify the endpoint against. The above two options should be made available for each individual channel of config_type webhook.

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