Add getInviteUrl extension for PartialApplications

lib/nyxx_extensions.dart

@@ -30,3 +30,4 @@ export 'src/extensions/role.dart';
 export 'src/extensions/scheduled_event.dart';
 export 'src/extensions/snowflake_entity.dart';
 export 'src/extensions/user.dart';
+export 'src/extensions/application.dart';

lib/src/extensions/application.dart

@@ -0,0 +1,23 @@
+import 'package:nyxx/nyxx.dart';
+
+/// Extensions on [PartialApplication]s.
+extension ApplicationExtensions on PartialApplication {
+  /// Get a URL users can visit to add this bot to a guild.
+  Uri getInviteUri({
+    List<String> scopes = const ['bot', 'application.commands'],
+    Flags<Permissions>? permissions,
+    Snowflake? guildId,
+    bool? disableGuildSelect,
+  }) =>
+      Uri.https(
+        'discord.com',
+        '/oauth2/authorize',
+        {
+          'client_id': id.toString(),
+          'scope': scopes.join(' '),
+          if (permissions != null) 'permissions': permissions.value.toString(),
+          if (guildId != null) 'guild_id': guildId.toString(),
+          if (disableGuildSelect != null) 'disable_guild_select': disableGuildSelect,
+        },
+      );
+}