Update sort details for Files endpoint

Author: MatthewSteeples

xero_files.yaml

@@ -45,11 +45,20 @@ paths:
           description: values to sort by
           schema:
             type: string
-            enum: 
-            - Name
-            - Size
-            - CreatedDateUTC
-            example: "CreatedDateUTC DESC"
+            enum:
+              - Name
+              - Size
+              - CreatedDateUTC
+            example: CreatedDateUTC
+        - in: query
+          name: direction
+          description: sort direction
+          schema:
+            type: string
+            enum:
+              - ASC
+              - DESC
+            example: ASC
       responses:
         '200':
           description: search results matching criteria