fix(model): simplify Config.ParentKey condition; add propagation test

- Restructure the ErrMultipleParents guard from a double-negative into a
  positive if/else — same semantics, more readable at a glance
- Add TestConfig_ParentKey_MultipleParentsPropagatesForNonVariables: uses
  two SchedulerForRelation entries (whose checkDefinedOn has no component-ID
  guard) to verify that ErrMultipleParents is propagated for non-variables
  component types, preventing future refactors from accidentally widening
  the fallback

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Matovidlo

internal/pkg/model/object.go

@@ -602,11 +602,14 @@ func (c *Config) ParentKey() (Key, error) {
 	if err == nil && parentKey != nil {
 		return parentKey, nil
 	}
-	if err != nil && (!errors.Is(err, ErrMultipleParents) || c.ComponentID != keboola.VariablesComponentID) {
+	if err != nil {
+		if errors.Is(err, ErrMultipleParents) && c.ComponentID == keboola.VariablesComponentID {
+			// Shared variables config with multiple consumers — fall back to structural parent.
+			return c.ConfigKey.ParentKey()
+		}
 		return nil, err
 	}
-	// No relation-defined parent, or shared variables config with multiple consumers —
-	// fall back to the structural parent (branch).
+	// No relation-defined parent — fall back to the structural parent (branch).
 	return c.ConfigKey.ParentKey()
 }
 

internal/pkg/model/object_test.go

@@ -109,6 +109,23 @@ func TestConfig_ParentKey_MultipleParentsFallsBackToBranch(t *testing.T) {
 	assert.Equal(t, BranchKey{ID: 1}, parentKey)
 }
 
+func TestConfig_ParentKey_MultipleParentsPropagatesForNonVariables(t *testing.T) {
+	t.Parallel()
+	// SchedulerForRelation.checkDefinedOn only requires a ConfigKey (no component-ID check),
+	// so two entries on the same config reach the multi-parents sentinel without being
+	// rejected by a component guard first.
+	cfg := &Config{
+		ConfigKey: ConfigKey{BranchID: 1, ComponentID: keboola.SchedulerComponentID, ID: "3"},
+		Relations: Relations{
+			&SchedulerForRelation{ComponentID: "ex-generic-v2", ConfigID: "1"},
+			&SchedulerForRelation{ComponentID: "ex-generic-v2", ConfigID: "2"},
+		},
+	}
+	_, err := cfg.ParentKey()
+	require.Error(t, err)
+	assert.ErrorIs(t, err, ErrMultipleParents)
+}
+
 func TestBranchMetadata_DeleteTemplateUsage(t *testing.T) {
 	t.Parallel()