FEAT: new ForeignDocumentUUIDField

FIX: Remove unnecessary fields
FEAT: use ForeignDocumentUUIDField in the Item Class DataModel

module/data/fields/foreignDocumentUUIDField.mjs

@@ -0,0 +1,30 @@
+/**
+ * A class extending DocumentUUIDField to allow selecting a foreign document reference
+ * that resolves to either the document, the index(for items in compenidums) or the UUID string.
+ */
+export default class ForeignDocumentUUIDField extends foundry.data.fields.DocumentUUIDField {
+  static get _defaults() {
+    return foundry.utils.mergeObject(super._defaults, {
+      nullable: true,
+      readonly: false,
+      idOnly: false,
+    });
+  }
+
+  initialize(value, _model, _options = {}) {
+    if (this.idOnly) return value;
+    return () => {
+      try {
+        const doc = fromUuidSync(value);
+        return doc;
+      } catch (error) {
+        console.error(error);
+        return value ?? null;
+      }
+    };
+  }
+
+  toObject(value) {
+    return value?.uuid ?? value;
+  }
+}