YAML tags: Let it be a string seperated by spaces and have a #

In general we try to follow the same format as specified in the input
note.

lib/core/note_serializer.dart

@@ -23,6 +23,9 @@ class NoteSerializationSettings {
   String typeKey = "type";
   String tagsKey = "tags";
 
+  bool tagsInString = false;
+  bool tagsHaveHash = false;
+
   bool saveTitleAsH1 = true;
 }
 
@@ -83,6 +86,13 @@ class NoteSerializer implements NoteSerializerInterface {
       data.props.remove(settings.tagsKey);
     } else {
       data.props[settings.tagsKey] = note.tags.toList();
+      if (settings.tagsInString) {
+        var tags = note.tags;
+        if (settings.tagsHaveHash) {
+          tags = tags.map((e) => '#$e').toSet();
+        }
+        data.props[settings.tagsKey] = tags.join(' ');
+      }
     }
 
     note.extraProps.forEach((key, value) {
@@ -191,7 +201,15 @@ class NoteSerializer implements NoteSerializerInterface {
           } else if (tags is List) {
             note.tags = tags.map((t) => t.toString()).toSet();
           } else if (tags is String) {
-            note.tags = {tags};
+            settings.tagsInString = true;
+            var allTags = tags.split(' ');
+            settings.tagsHaveHash = allTags.every((t) => t.startsWith('#'));
+            if (settings.tagsHaveHash) {
+              allTags.removeWhere((e) => e.length <= 1);
+              allTags = allTags.map((e) => e.substring(1)).toList();
+            }
+
+            note.tags = allTags.toSet();
           } else {
             Log.e("Note Tags Decoding Failed: $tags");
           }

test/note_serializer_test.dart

@@ -123,11 +123,11 @@ void main() {
       expect(doc.props['draft'], true);
     });
 
-    test('Test Non list Tag', () {
+    test('Test string tag with #', () {
       var props = LinkedHashMap<String, dynamic>.from(<String, dynamic>{
         "title": "Why not?",
         "draft": true,
-        "tags": "foo",
+        "tags": "#foo #bar-do",
       });
       var doc = MdYamlDoc("body", props);
 
@@ -140,13 +140,13 @@ void main() {
       expect(note.body, "body");
       expect(note.title, "Why not?");
       expect(note.extraProps, <String, dynamic>{"draft": true});
-      expect(note.tags, <String>{"foo"});
+      expect(note.tags, <String>{"foo", "bar-do"});
 
       serializer.encode(note, doc);
       expect(doc.body, "body");
       expect(doc.props['title'], 'Why not?');
       expect(doc.props['draft'], true);
-      expect(doc.props['tags'], ['foo']);
+      expect(doc.props['tags'], "#foo #bar-do");
       expect(doc.props.length, 3);
     });
   });