Implemented editable album title (#130)

* Replace static title text with a text edit field
* Implement endpoint for updating album info
* Implement changing title
* Only the owner can change the title

mobile/lib/modules/sharing/models/album_viewer_page_state.model.dart

@@ -0,0 +1,53 @@
+import 'dart:convert';
+
+class AlbumViewerPageState {
+  final bool isEditAlbum;
+  final String editTitleText;
+  AlbumViewerPageState({
+    required this.isEditAlbum,
+    required this.editTitleText,
+  });
+
+  AlbumViewerPageState copyWith({
+    bool? isEditAlbum,
+    String? editTitleText,
+  }) {
+    return AlbumViewerPageState(
+      isEditAlbum: isEditAlbum ?? this.isEditAlbum,
+      editTitleText: editTitleText ?? this.editTitleText,
+    );
+  }
+
+  Map<String, dynamic> toMap() {
+    final result = <String, dynamic>{};
+
+    result.addAll({'isEditAlbum': isEditAlbum});
+    result.addAll({'editTitleText': editTitleText});
+
+    return result;
+  }
+
+  factory AlbumViewerPageState.fromMap(Map<String, dynamic> map) {
+    return AlbumViewerPageState(
+      isEditAlbum: map['isEditAlbum'] ?? false,
+      editTitleText: map['editTitleText'] ?? '',
+    );
+  }
+
+  String toJson() => json.encode(toMap());
+
+  factory AlbumViewerPageState.fromJson(String source) => AlbumViewerPageState.fromMap(json.decode(source));
+
+  @override
+  String toString() => 'AlbumViewerPageState(isEditAlbum: $isEditAlbum, editTitleText: $editTitleText)';
+
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) return true;
+
+    return other is AlbumViewerPageState && other.isEditAlbum == isEditAlbum && other.editTitleText == editTitleText;
+  }
+
+  @override
+  int get hashCode => isEditAlbum.hashCode ^ editTitleText.hashCode;
+}