fix: prevent panic when schemaregistry is configured without an auth provider (#1424)

* Add TestNoAuthProviderSetAuthenticationHeaders to demonstrate panic when no auth provider is set in schemaregistry client config

* Add early return to SetAuthenticationHeaders when provider is nil

---------

Co-authored-by: Robert Yokota <[email protected]>

Author: maheperera

schemaregistry/internal/rest_service.go

@@ -456,6 +456,9 @@ func (rs *RestService) HandleRequest(request *API, response interface{}) error {
 
 // SetAuthenticationHeaders sets the authentication headers on the request
 func SetAuthenticationHeaders(provider AuthenticationHeaderProvider, headers *http.Header) error {
+	if provider == nil {
+		return nil
+	}
 	authHeader, err := provider.GetAuthenticationHeader()
 	if err != nil {
 		return err

schemaregistry/internal/rest_service_test.go

@@ -315,3 +315,19 @@ func TestSetAuthenticationHandlers(t *testing.T) {
 		t.Errorf("should have Confluent-Identity-Pool-Id header with value pool_id")
 	}
 }
+
+func TestNoAuthProviderSetAuthenticationHeaders(t *testing.T) {
+	config := &ClientConfig{}
+
+	rs, err := NewRestService(config)
+
+	if err != nil {
+		t.Errorf("should work with no auth provider")
+	}
+
+	err = SetAuthenticationHeaders(config.AuthenticationHeaderProvider, &rs.headers)
+
+	if err != nil {
+		t.Errorf("should work with no auth provider, got err %s", err)
+	}
+}