Add oauth_validation support for user access token requests

[mdailey]

The OAuth 1.0a specification provides for a field <oauth_verifier> to be included in the signature body and sent in the Authorization header. This PR adds support for this field. It is needed for the Garmin Connect API and perhaps others.

[pavinduLakshan]

I needed oauth_verifier to be included to make things work as expected in Magento 2 API but eventually had to implement it on my own. This is quite important, but missing feature in this package. Someone responsible please have a look at this MR 🙏