Add token processor plugin support (#4059)

* Add token processor plugin support

* fix import

* fix import

fastdeploy/plugins/token_processor/__init__.py

@@ -0,0 +1,27 @@
+"""
+# Copyright (c) 2025  PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+
+from fastdeploy.plugins.utils import load_plugins_by_group
+
+# make sure one process only loads plugins once
+PLUGINS_GROUP = "fastdeploy.token_processor_plugins"
+
+
+def load_token_processor_plugins():
+    """load_token_processor_plugins"""
+    plugins = load_plugins_by_group(group=PLUGINS_GROUP)
+    assert len(plugins) <= 1, "Most one plugin is allowed to be loaded."
+    return next(iter(plugins.values()))()