generate_upload_token: Refactor code to use 'optional_keys' list.

Process optional parameters like it is done in method "perform_upload", this
will allow the introduction of more optional parameter.

pydas/drivers.py

@@ -922,7 +922,7 @@ def create_link(self, token, folder_id, url, **kwargs):
         response = self.request('midas.link.create', parameters)
         return response
 
-    def generate_upload_token(self, token, item_id, filename, checksum=None):
+    def generate_upload_token(self, token, item_id, filename, **kwargs):
         """
         Generate a token to use for upload.
 
@@ -953,8 +953,10 @@ def generate_upload_token(self, token, item_id, filename, checksum=None):
         parameters['token'] = token
         parameters['itemid'] = item_id
         parameters['filename'] = filename
-        if checksum is not None:
-            parameters['checksum'] = checksum
+        optional_keys = ['checksum']
+        for key in optional_keys:
+            if key in kwargs:
+                parameters[key] = kwargs[key]
         response = self.request('midas.upload.generatetoken', parameters)
         return response['token']