Probe every access review connector on status check

Bad API keys and expired OAuth tokens showed Connected because
probes ran only for OAuth2 and many providers had no ProbeURL.
Add a registry ProbeConnection dispatcher with static, dynamic,
and custom probes so all 41 providers are checked on demand.

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/connector/provider/tailscale.go

@@ -28,6 +28,7 @@ func tailscaleRegistration() *Registration {
 		Provider:       coredata.ConnectorProviderTailscale,
 		DisplayName:    "Tailscale",
 		SupportsAPIKey: true,
+		ProbeURL:       "https://api.tailscale.com/api/v2/tailnet/-/users",
 		NewDriver: func(_ context.Context, c *http.Client, _ *coredata.Connector, _ *log.Logger) (drivers.Driver, error) {
 			return drivers.NewTailscaleDriver(c), nil
 		},