test: add regression test for explicit null required param

internal/util/parameters/parameters.go

@@ -144,7 +144,7 @@ func ParseParams(ps Parameters, data map[string]any, claimsMap map[string]map[st
 			// parse non auth-required parameter
 			var ok bool
 			v, ok = data[name]
-			if !ok {
+			if !ok || v == nil {
 				v = p.GetDefault()
 				// if the parameter is required and no value given, throw an error
 				if CheckParamRequired(p.GetRequired(), v) {

internal/util/parameters/parameters_test.go

@@ -2347,3 +2347,23 @@ func TestCheckParamRequired(t *testing.T) {
 		})
 	}
 }
+
+func TestParseParams_ExplicitNullForRequiredParam(t *testing.T) {
+	// Define a required string parameter
+	params := parameters.Parameters{
+		parameters.NewStringParameter("required_param", "this is required"),
+	}
+
+	// Input map with explicit nil
+	input := map[string]any{
+		"required_param": nil,
+	}
+
+	// Call ParseParams
+	_, err := parameters.ParseParams(params, input, nil)
+
+	// Expect an error because the parameter is required
+	if err == nil {
+		t.Errorf("ParseParams allowed explicit nil for required parameter, expected error")
+	}
+}