Added support of JWT tokens.

[volodymyr-chekyrta]

By default, access tokens are now in JWT format.
The type of access token can be changed in the Core.Config class.

Supported token types are represented by the TokenType enum.

enum TokenType: String {
    case jwt = "JWT"
    case bearer = "BEARER"
}

[openedx-webhooks]

Although this pull request is already merged, I'm still watching it for updates.

There is nothing you have to do. No action is needed from your side. Thanks again for your contribution.