API: Modify tool calling for wider compat

When revisiting tool calls, the formats have more or less become standard.
For greater compatibility with templates, primarily use the message.tools
parameter and remove the extra custom metadata that is no longer required.

However, unlike other backends, tabbyAPI still uses template metadata
to declare what the tool start string is. This allows for template-level
customization along with giving more power to the user while the server
exists to consume rather than work on a case-by-case basis.

Signed-off-by: kingbri <8082010+kingbri1@users.noreply.github.com>

common/templating.py

@@ -4,6 +4,8 @@ import traceback
 import aiofiles
 import json
 import pathlib
+from dataclasses import dataclass, field
+from datetime import datetime
 from importlib.metadata import version as package_version
 from typing import List, Optional
 from jinja2 import Template, TemplateError
@@ -11,7 +13,6 @@ from jinja2.ext import loopcontrols
 from jinja2.sandbox import ImmutableSandboxedEnvironment
 from loguru import logger
 from packaging import version
-from datetime import datetime
 
 
 from common.utils import unwrap
@@ -23,11 +24,12 @@ class TemplateLoadError(Exception):
     pass
 
 
+@dataclass
 class TemplateMetadata:
     """Represents the parsed metadata from a template."""
 
-    stop_strings: List[str] = []
-    tool_starts: List[str] = []
+    stop_strings: List[str] = field(default_factory=list)
+    tool_start: Optional[str] = None
 
 
 class PromptTemplate:
@@ -72,11 +74,7 @@ class PromptTemplate:
 
         if hasattr(template_module, "tool_start"):
             if isinstance(template_module.tool_start, str):
-                template_metadata.tool_starts.append(template_module.tool_start)
-
-        if hasattr(template_module, "tool_start_token"):
-            if isinstance(template_module.tool_start_token, int):
-                template_metadata.tool_starts.append(template_module.tool_start_token)
+                template_metadata.tool_start = template_module.tool_start
 
         self.metadata = template_metadata
         return template_metadata