Alerting: Fix Teams notifier not failing on 200 response with error (#52254)

Team's webhook API does not always use the status code to communicate errors.
There are cases where it returns 200 and an error message in the body.
For example, 429 - Too Many Requests or when the message is too large.
Instead, what we should be looking for is a response body = "1".

https://docs.microsoft.com/en-us/microsoftteams/platform/webhooks-and-connectors/how-to/connectors-using?tabs=cURL#send-messages-using-curl-and-powershell

pkg/models/notifications.go

@@ -41,6 +41,7 @@ type SendWebhookSync struct {
 	HttpMethod  string
 	HttpHeader  map[string]string
 	ContentType string
+	Validation  func(body []byte, statusCode int) error
 }
 
 type SendResetPasswordEmailCommand struct {