Add webhook resource

[kyle-mcguire]

Callouts

• It took some tinkering for me to get the authentication block working. Let me know if there is a better way of doing that
• The credentials in the auth type are all listed as optional even when they are required depending on the selected auth type. This means that webhook resources could be misconfigured in TF and at runtime a webhook resource update could delete a webhook and be unable to recreate it. Is there a better way to define these union types?
• Do the optional parameters for CreateWebhook look like idiomatic Go?
• id and slug both appear in the the TF plan. Is that expected or am I mapping the id to slug incorrectly somewhere?

Terraform used the selected providers to generate the following execution plan. Resource actions
are indicated with the following symbols:
-/+ destroy and then create replacement

Terraform will perform the following actions:

  # doppler_webhook.ci must be replaced
-/+ resource "doppler_webhook" "ci" {
      ~ id              = "a8796e6f-1dc3-4997-a0c4-4772e5a79a3a" -> (known after apply)
      ~ payload         = (sensitive value) # forces replacement
      ~ slug            = "a8796e6f-1dc3-4997-a0c4-4772e5a79a3a" -> (known after apply)
        # (5 unchanged attributes hidden)

        # (1 unchanged block hidden)
    }

Plan: 1 to add, 0 to change, 1 to destroy.