fix: Filter out cust. AssumeRole Token for audit (#19646)

The `Token` parameter is a sensitive value that should not be output in the Audit log for STS AssumeRoleWithCustomToken API.

Bonus: Add a simple tool that echoes audit logs to the console.

docs/iam/identity-manager-plugin.go

@@ -81,6 +81,6 @@ func mainHandler(w http.ResponseWriter, r *http.Request) {
 func main() {
 	http.HandleFunc("/", mainHandler)
 
-	log.Print("Listing on :8081")
+	log.Print("Listening on :8081")
 	log.Fatal(http.ListenAndServe(":8081", nil))
 }