[client] Assert the MDM upload URL never leaks into the debug bundle

Populate DebugBundleUploadURL with a token-bearing value and assert the
rendered bundle contains neither the field name nor the token, in both
anonymize modes. The excluded-map entry only skips the missing-field
check; this guards against the value being serialized by a future change.

client/internal/debug/debug_test.go

@@ -888,6 +888,7 @@ func TestAddConfig_AllFieldsCovered(t *testing.T) {
 		ClientCertPath:                "/tmp/cert",
 		ClientCertKeyPath:             "/tmp/key",
 		LazyConnection:                "on",
+		DebugBundleUploadURL:          "https://upload.example.test/bundle?token=secret",
 		MTU:                           1280,
 		DisableIPv6:                   true,
 		SyncMessageVersion:            func(v int) *int { return &v }(1),
@@ -905,6 +906,13 @@ func TestAddConfig_AllFieldsCovered(t *testing.T) {
 			g.addCommonConfigFields(&sb)
 			rendered := sb.String() + renderAddConfigSpecific(g)
 
+			// DebugBundleUploadURL is an MDM-provided value that can carry
+			// credentials or signed query tokens. It is deliberately excluded
+			// above; assert it never reaches the rendered bundle — neither the
+			// field name nor the token — in either anonymize mode.
+			assert.NotContains(t, rendered, "DebugBundleUploadURL:", "MDM upload URL field must not be serialized into the debug bundle")
+			assert.NotContains(t, rendered, "token=secret", "MDM upload URL value must not leak into the debug bundle")
+
 			val := reflect.ValueOf(cfg).Elem()
 			typ := val.Type()
 			var missing []string