[Feature request] Add/Remove tags to Hydrus database item

[GreenLandisaLie]

I managed to add this feature in my private cloned repo. This is the cleaned version of the main method I use:

Future AddOrRemoveTags(BooruItem item, List<String> tagsList, bool isTagsToRemove) async {
  	String url = "${booru.baseURL}/add_tags/add_tags";
  	var dio = Dio();
	// notes: "my tags" works
	// "all known tags" does not work -.-
	// 0 to add
	// 1 to delete
	String addOrRemove = isTagsToRemove ? "1" : "0";
	Response dioResponse = await dio.post(url,
		options: Options(headers: {
			HttpHeaders.contentTypeHeader: "application/json",
			"Hydrus-Client-API-Access-Key":booru.apiKey!
		}),
		data: jsonEncode({
			"hash": item.md5String,
			"service_names_to_actions_to_tags": {
				"my tags": {
					"$addOrRemove": tagsList
				}
			}
		}),
	);
	return fetched;
}

(for reference) I've implemented this 2 ways: 1 - I copied the share toolbar button and added a bunch of options for the tags I most commonly edit. When I click the button it will ADD the (selected) tag and when I hold it REMOVES it. Just like the share button this setting is saveable and the default action can be set in the settings (however I'm using hard-coded tags - in a public release the user should be able to set which tags they want to show up in the options). The top option is not a defined tag and instead it will prompt the user for a text (tag) - I did that following this basic tutorial. 2 - I added 2 buttons that show up when the user holds on a tag in the TagView.

EDIT: maybe change the first arg to a list of BooruItem and create a List<String> of the item's hashes to be sent in the POST for when the user might want to use this feature from within the main window (when multiple items are selected).