Return token content when refreshing token

[lan17]

When refreshing token, I would like to actually get the token contents so I can store it for offline usage. To this end, I added return statement to refresh_access_token method.

Checklist

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• Non-code related change (markdown/git settings etc)
• SDK Code Change
• Example/Test Code Change

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• Does tox pass?
• Do the tests pass?

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[greg-db]

Thanks for submitting this! I'll ask the team to review it.