Fix Heroku connection probe Accept header

Heroku's connection-status probe used a static ProbeURL, which the
generic probe issues with `Accept: application/json`. Heroku negotiates
the API version through the Accept media type and returns 400 for an
unversioned request, which doProbeRequest reads as "connected" -- so the
probe never caught a revoked token (it only surfaced at the first
ListAccounts).

Probe via a probeHeroku closure that sends
`Accept: application/vnd.heroku+json; version=3` instead. Verified live:
a dead token returns 400 with application/json but 401 with the
versioned header, which doProbeRequest correctly maps to rejected.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

pkg/connector/provider/heroku.go

@@ -26,11 +26,14 @@ import (
 
 func herokuRegistration() *Registration {
 	return &Registration{
-		Provider:     coredata.ConnectorProviderHeroku,
-		DisplayName:  "Heroku",
-		AuthURL:      "https://id.heroku.com/oauth/authorize",
-		TokenURL:     "https://id.heroku.com/oauth/token",
-		ProbeURL:     "https://api.heroku.com/account",
+		Provider:    coredata.ConnectorProviderHeroku,
+		DisplayName: "Heroku",
+		AuthURL:     "https://id.heroku.com/oauth/authorize",
+		TokenURL:    "https://id.heroku.com/oauth/token",
+		// Heroku requires the versioned Accept header; a plain ProbeURL GET
+		// (Accept: application/json) returns 400 and would read as connected,
+		// so probe via a closure that sends application/vnd.heroku+json.
+		Probe:        probeHeroku,
 		OAuth2Scopes: []string{"read"},
 		NewDriver: func(_ context.Context, c *http.Client, conn *coredata.Connector, _ *log.Logger) (drivers.Driver, error) {
 			s, err := coredata.ConnectorSettings[coredata.HerokuConnectorSettings](conn)