tailcfg: update rename SSHFailureNotifyRequest and add EventType

This change renames SSHFailureNotifyRequest to SSHEventNotifyRequest
to better reflect the additional events we could add in the future.
This change also adds an EventType used to catagories the events.

Updates tailscale/corp#9967

Signed-off-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>

tailcfg/tailcfg.go

@@ -2075,9 +2075,11 @@ type SSHRecorderFailureAction struct {
 	NotifyURL string `json:",omitempty"`
 }
 
-// SSHRecordingFailureNotifyRequest is the JSON payload sent to the NotifyURL
-// when a recording fails.
-type SSHRecordingFailureNotifyRequest struct {
+// SSHEventNotifyRequest is the JSON payload sent to the NotifyURL
+// for an SSH event.
+type SSHEventNotifyRequest struct {
+	// EventType is the type of notify request being sent.
+	EventType SSHEventType
 	// CapVersion is the client's current CapabilityVersion.
 	CapVersion CapabilityVersion
 
@@ -2093,10 +2095,19 @@ type SSHRecordingFailureNotifyRequest struct {
 	// LocalUser is the user that was resolved from the SSHUser for the local machine.
 	LocalUser string
 
-	// Attempts is the list of recorders that were attempted, in order.
-	Attempts []SSHRecordingAttempt
+	// RecordingAttempts is the list of recorders that were attempted, in order.
+	RecordingAttempts []*SSHRecordingAttempt
 }
 
+// SSHEventType defines the event type linked to a SSH action or state.
+type SSHEventType int
+
+const (
+	UnspecifiedSSHEventType       SSHEventType = 0
+	SSHSessionRecordingRejected   SSHEventType = 1
+	SSHSessionRecordingTerminated SSHEventType = 2
+)
+
 // SSHRecordingAttempt is a single attempt to start a recording.
 type SSHRecordingAttempt struct {
 	// Recorder is the address of the recorder that was attempted.