Begin giant move terms function with test of named parameters

As we move this function in from custom code.

migration_helpers.info.yml

@@ -2,3 +2,4 @@ name: Migration Helpers
 type: module
 description: Provides helpers to migrate data into modern Drupal.
 core_version_requirement: ^9 || ^10
+php: 8.0

migration_helpers.module

@@ -3,18 +3,25 @@
 /**
  * Entity query helper.
  */
-function migration_helpers_entity_query($entity_type, $bundle, $field = '') {
+function migration_helpers_entity_query(
+  $entity_type = 'node',
+  $bundle = NULL,
+  $field = NULL,
+) {
 
   /** @var \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager */
   $entity_type_manager = \Drupal::service('entity_type.manager');
 
   $entity_storage = $entity_type_manager->getStorage($entity_type);
-  $bundle_key = $entity_storage->getEntityType()->getKey('bundle');
 
   $entity_query = $entity_storage->getQuery();
-  $entity_query->condition($bundle_key, $bundle);
 
-  if (!empty($field)) {
+  if ($bundle) {
+    $bundle_key = $entity_storage->getEntityType()->getKey('bundle');
+    $entity_query->condition($bundle_key, $bundle);
+  }
+
+  if ($field) {
     // Check that field BOTH is present on entity bundle AND has a value saved.
     $entity_query->exists($field);
   }
@@ -27,6 +34,33 @@ function migration_helpers_entity_query($entity_type, $bundle, $field = '') {
 
 }
 
+/**
+ * Move (and optionally filter/transform) terms between term reference fields.
+ */
+function migration_helpers_move_terms(
+  $source_vocabulary,
+  $destination_vocabulary,
+  $source_field,
+  $destination_field,
+  $source_bundle,
+  $destination_bundle = NULL,
+  $source_entity_type = 'node',
+  $destination_entity_type = 'node',
+  $mapping = [],
+) {
+  // Destination bundle is also required but we default to making it
+  // the same as the source bundle.
+  $destination_bundle ??= $source_bundle;
+    print("
+    $source_entity_type,
+    $source_bundle,
+    $source_field,
+    $destination_entity_type,
+    $destination_bundle,
+    $destination_field,
+    $source_vocabulary,
+    $destination_vocabulary");
+}
 
 // The below almost serve more as examples that can be followed