Fixed grant_type for refresh_token_request(). You don't need to manually change grant_type before starting the func and change it back after.
Added the ability to expand the code base for obtaining an access token with different grant types (Authorization Code Grant, Resource Owner Password Credentials Grant, Implicit Grant, etc.)
Implemented getting access token using Resource Owner Password Credentials Grant.
Added tests
Updated README
Added blank lines to function descriptions (Popular IDE PyCharm can't separate description from params without it when describing function).
Before:
After:
Changes
Notes
This PR does not break backward compatibility.