Include required grant_type parameter in docs for refreshing oauth tokens

This parameter is required for the refresh request to succeed, but is
absent from the documentation at present.

Author: Dorthu

openapi.yaml

@@ -84,7 +84,7 @@ info:
     | 4.  The login server redirects the user to the specificed redirect URL with a temporary authorization `code` (exchange code) in the URL. | 4.  The login server redirects the user back to your application with an OAuth `access_token` embedded in the redirect URL's hash. This is temporary and expires in two hours. No `refresh_token` is issued. Therefore, once the `access_token` expires, a new one will need to be issued by having the user log in again. |
     | 5.  The application issues a POST request (*see below*) to the login server with the exchange code, `client_id`, and the client application's `client_secret`. | |
     | 6.  The login server responds to the client application with a new OAuth `access_token` and `refresh_token`. The `access_token` is set to expire in two hours. | |
-    | 7.  The `refresh_token` can be used by contacting the login server with the `client_id`, `client_secret`, and `refresh_token` to get a new OAuth `access_token` and `refresh_token`. The new `access_token` is good for another two hours, and the new `refresh_token`, can be used to extend the session again by this same method. | |
+    | 7.  The `refresh_token` can be used by contacting the login server with the `client_id`, `client_secret`, `grant_type`, and `refresh_token` to get a new OAuth `access_token` and `refresh_token`. The new `access_token` is good for another two hours, and the new `refresh_token`, can be used to extend the session again by this same method. | |
 
     ### OAuth Private Workflow - Additional Details
 
@@ -103,6 +103,7 @@ info:
 
     | PARAMETER | DESCRIPTION |
     |-----------|-------------|
+    | grant_type | The grant type you're using for renewal.  Currently only the string "refresh_token" is accepted. |
     | client_id | Your app's client ID. |
     | client_secret | Your app's client secret. |
     | code | The code you just received from the redirect. |