Auto-authorize if valid refresh tokens exist

[madprime]

This implements a check on refresh tokens for auto skipping of the authorization form, as described in #753.

[coveralls]

Pull Request Test Coverage Report for Build 1185

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.008%) to 94.689%

---

Totals
Change from base Build 1167:	0.008%
Covered Lines:	1248
Relevant Lines:	1318

---

💛 - Coveralls

[auvipy]

thanks for the PR. you also need to add test for this

[madprime]

@auvipy thanks, added a test which would have previously failed, and passes now. see what you think?

[n2ygk]

@madprime @auvipy I'm trying to document PRs merged between 1.2.0 and forthcoming 1.3.0 (#785) that did not make it into the CHANGELOG.md. Can you provide a one-line explanation of this feature. Is it a bug fix or added feature? Also, is this something to be documented in docs/? A documentation PR which would greatly appreciated if so.

I don't quite understand how this automatic use of Refresh Token is used. Is there a reference to the OAuth2 RFCs?

Thanks.

[auvipy]

according to #753 (comment) and another WIP PR, I think we should revert this for now.

[auvipy]

please check #755