Fix upload_attachment (#270)

## 📝 Description

closes #17 

Fix `upload_attachment` method of `SupportTicket` class.

## ✔️ How to Test

Manually test it

Author: zliang-akamai

linode_api4/objects/support.py

@@ -1,3 +1,6 @@
+from pathlib import Path
+from typing import Union
+
 import requests
 
 from linode_api4.errors import ApiError, UnexpectedResponseError
@@ -139,7 +142,7 @@ def post_reply(self, description):
         r = TicketReply(self._client, result["id"], self.id, result)
         return r
 
-    def upload_attachment(self, attachment):
+    def upload_attachment(self, attachment: Union[Path, str]):
         """
         Uploads an attachment to an existing Support Ticket.
 
@@ -151,27 +154,25 @@ def upload_attachment(self, attachment):
         :returns: Whether the upload operation was successful.
         :rtype: bool
         """
+        if not isinstance(attachment, Path):
+            attachment = Path(attachment)
 
-        content = None
-        with open(attachment) as f:
-            content = f.read()
-
-        if not content:
-            raise ValueError("Nothing to upload!")
+        if not attachment.exists():
+            raise ValueError("File not exist, nothing to upload.")
 
         headers = {
-            "Authorization": "token {}".format(self._client.token),
-            "Content-type": "multipart/form-data",
+            "Authorization": "Bearer {}".format(self._client.token),
         }
 
-        result = requests.post(
-            "{}{}/attachments".format(
-                self._client.base_url,
-                SupportTicket.api_endpoint.format(id=self.id),
-            ),
-            headers=headers,
-            files=content,
-        )
+        with open(attachment, "rb") as f:
+            result = requests.post(
+                "{}{}/attachments".format(
+                    self._client.base_url,
+                    SupportTicket.api_endpoint.format(id=self.id),
+                ),
+                headers=headers,
+                files={"file": f},
+            )
 
         if not result.status_code == 200:
             errors = []