refactor(newappeal): extract file merge and dedupe helpers (Slice 2b)

lib/newappeal/fileListHelpers.js

@@ -0,0 +1,28 @@
+export const mergeWithExistingFilesList = (buildAppealFilesArray, values) => {
+    return values.hasOwnProperty("filesList")
+        ? (buildAppealFilesArray.concat(values.filesList),
+          buildAppealFilesArray.filter(function (item, idx) {
+              return item.name;
+          }))
+        : buildAppealFilesArray;
+};
+
+export const removeDuplicatesByKey = (arr, key) => {
+    const seen = new Set();
+    return arr.filter((item) => {
+        const value = item[key];
+        if (seen.has(value)) {
+            return false; // Duplicate found
+        } else {
+            seen.add(value); // Add value to the set
+            return true; // Keep the item
+        }
+    });
+};
+
+export const dedupeFilesListByName = (filesList) => {
+    return filesList.filter(
+        (value, index, self) =>
+            index === self.findIndex((t) => t.name === value.name)
+    );
+};