server : Add option to return token pieces in /tokenize endpoint (#9108)

* server : added with_pieces functionality to /tokenize endpoint

* server : Add tokenize with pieces tests to server.feature

* Handle case if tokenizer splits along utf8 continuation bytes

* Add example of token splitting

* Remove trailing ws

* Fix trailing ws

* Maybe fix ci

* maybe this fix windows ci?

---------

Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

.github/workflows/server.yml

@@ -173,6 +173,7 @@ jobs:
         if: ${{ !matrix.disabled_on_pr || !github.event.pull_request }}
         run: |
           cd examples/server/tests
+          $env:PYTHONIOENCODING = ":replace"
           behave.exe --summary --stop --no-capture --exclude 'issues|wrong_usages|passkey' --tags llama.cpp
 
       - name: Slow tests