feat: allow guidance backend for V0

Signed-off-by: Travis Johnson <[email protected]>

Author: tjohnson31415

vllm/config.py

@@ -3094,7 +3094,7 @@ def get_served_model_name(model: str,
 
 
 GuidedDecodingBackendV0 = Literal["auto", "outlines", "lm-format-enforcer",
-                                  "xgrammar"]
+                                  "xgrammar", "guidance"]
 GuidedDecodingBackendV1 = Literal["auto", "xgrammar", "guidance"]