TF-3996 Group context menu actions when opened email

core/lib/presentation/extensions/iterable_extension.dart

@@ -0,0 +1,44 @@
+extension IterableExtension<T> on Iterable<T> {
+  /// Group elements by [keySelector].
+  /// If [sortKeys] = true, the keys will be sorted in ascending order,
+  /// key == -1 will always be at the bottom (applies to int keys).
+  Map<K, List<T>> groupBy<K>(
+    K Function(T element) keySelector, {
+    bool sortKeys = false,
+  }) {
+    final map = <K, List<T>>{};
+    for (final element in this) {
+      final key = keySelector(element);
+      map.putIfAbsent(key, () => []).add(element);
+    }
+
+    Iterable<K> sortedKeys;
+
+    if (sortKeys && K == int) {
+      sortedKeys = map.keys.toList()
+        ..sort((a, b) {
+          final ai = a as int;
+          final bi = b as int;
+          if (ai == -1 && bi != -1) return 1;
+          if (bi == -1 && ai != -1) return -1;
+          return ai.compareTo(bi);
+        });
+    } else if (sortKeys) {
+      sortedKeys = map.keys.toList()
+        ..sort((a, b) {
+          if (a is Comparable && b is Comparable) {
+            return (a as Comparable).compareTo(b);
+          }
+          return 0;
+        });
+    } else {
+      sortedKeys = map.keys;
+    }
+
+    final result = <K, List<T>>{};
+    for (final key in sortedKeys) {
+      result[key] = map[key]!;
+    }
+    return result;
+  }
+}