Refresh access_token request added

[gassan]

Hey!

Type: new feature

• I have read and understood the Contributing Guidelines.
• I have checked that another pull request for this purpose does not exist.
• I wrote some tests for this PR.

Small description of change:

added request to refresh an access_token with an refresh_token.

Thanks 😺

[ovr]

Hello @gassan,

Thank you for your PR,

@ADmad Can you try this PR (big thanks)?

I cannot find any free time to test it.

[ADmad]

@ovr Sorry, I too am a bit busy right now and don't have a project using the lib handy currently to try out the changes.