Adding bearer token in compass (#16)

<!-- begin-generated-description -->

This pull request introduces a new `bearer_token` parameter to the
`__init__` method of the `compass_sdk/compass.py` file. The
`bearer_token` is an optional string that can be used for authentication
purposes.

The changes made in this PR are as follows:
- A new `bearer_token` parameter is added to the `__init__` method,
allowing for optional authentication using a bearer token.
- The `self.bearer_token` attribute is set to the value of the
`bearer_token` parameter.
- The `_send_request_with_retry` method is modified to include a check
for the `self.bearer_token`. If it exists, the request headers are
updated with the bearer token for authentication.

The PR enhances the authentication process by providing an alternative
to the existing username and password-based authentication. The bearer
token can be used to securely authenticate requests, offering a more
flexible and secure approach.

<!-- end-generated-description -->

compass_sdk/compass.py

@@ -75,6 +75,7 @@ def __init__(
         index_url: str,
         username: Optional[str] = None,
         password: Optional[str] = None,
+        bearer_token: Optional[str] = None,
         logger_level: LoggerLevel = LoggerLevel.INFO,
     ):
         """
@@ -87,6 +88,7 @@ def __init__(
         self.username = username or os.getenv("COHERE_COMPASS_USERNAME")
         self.password = password or os.getenv("COHERE_COMPASS_PASSWORD")
         self.session = requests.Session()
+        self.bearer_token = bearer_token
 
         self.function_call = {
             "create_index": self.session.put,
@@ -497,18 +499,23 @@ def _send_request(
         )
         def _send_request_with_retry():
             nonlocal error
+
             try:
+
+                data_dict = None
                 if data:
                     if isinstance(data, BaseModel):
                         data_dict = data.model_dump(mode="json")
                     elif isinstance(data, Dict):
                         data_dict = data
 
-                    response = self.function_call[function](
-                        target_path, json=data_dict, auth=(self.username, self.password)
-                    )
-                else:
-                    response = self.function_call[function](target_path, auth=(self.username, self.password))
+                headers = None
+                auth = (self.username, self.password)
+                if self.bearer_token:
+                    headers = {"Authorization": f"Bearer {self.bearer_token}"}
+                    auth = None
+
+                response = self.function_call[function](target_path, json=data_dict, auth=auth, headers=headers)
 
                 if response.ok:
                     error = None