feat: add support for copilot provider (#8577)

* feat: add support for copilot provider

* test: add tests for github copilot

* chore: clean up github copilot authenticator

* test: add test for github copilot authenticator

* test: add test for github copilot for sonnet 3.7 thought model

---------

Co-authored-by: Krish Dholakia <krrishdholakia@gmail.com>

litellm/llms/github_copilot/chat/transformation.py

@@ -0,0 +1,37 @@
+from typing import Optional, Tuple
+
+
+from litellm.llms.openai.openai import OpenAIConfig
+
+from ..authenticator import Authenticator
+from ..constants import GetAPIKeyError
+from litellm.exceptions import AuthenticationError
+
+
+class GithubCopilotConfig(OpenAIConfig):
+    def __init__(
+        self,
+        api_key: Optional[str] = None,
+        api_base: Optional[str] = None,
+        custom_llm_provider: str = "openai",
+    ) -> None:
+        super().__init__()
+        self.authenticator = Authenticator()
+
+    def _get_openai_compatible_provider_info(
+        self,
+        model: str,
+        api_base: Optional[str],
+        api_key: Optional[str],
+        custom_llm_provider: str,
+    ) -> Tuple[Optional[str], Optional[str], str]:
+        api_base = "https://api.githubcopilot.com"
+        try:
+            dynamic_api_key = self.authenticator.get_api_key()
+        except GetAPIKeyError as e:
+            raise AuthenticationError(
+                model=model,
+                llm_provider=custom_llm_provider,
+                message=str(e),
+            )
+        return api_base, dynamic_api_key, custom_llm_provider