Add id_token to TokenResponse

[xhanin]

Is your feature request related to a problem? Please describe.
It would be nice to be able to support OpenIDConnect ID Token in the TokenResponse issued by the authorize calls.

Describe the solution you'd like
Related to #50 which would allow to add custom metadata to AT and open the Identity information, it would be nice to be able to create an ID token in the Token response to comply with OIDC specification

Describe alternatives you've considered
The TokenResponse being closed and the conversion from AT to TokenResponse hard coded I see no other way to handle that, except relying on a ThreadLocal :(

[adhesivee]

Please check #53 if this supports your use-case

[xhanin]

Having metadata on Identity would help, but I would also need to have a way to add an id token to the token response.

So to support OIDC you would need to either:

• add an idToken property on TokenReponse or make it extensible, and give a way to customize the fun AccessToken.toTokenResponse extension method.
• add an idToken:String property to AccessToken and TokenResponse (copied from one to the other in AccessToken.toTokenResponse), so that one could fill it in the AccessTokenConverter.

[adhesivee]

Ah yeah, overlooked that part. I created #54 which will allow this.
This will give you the option to configure an access token responder in your configuration:

accessTokenResponder = object : AccessTokenResponder {
	override fun createResponse(accessToken: AccessToken): Map<String, Any?> =
            with(accessToken) {
                mapOf(
			"id_token" to "<YOUR_ID_TOKEN>",
                        "access_token" to this.accessToken,
                        "token_type" to this.tokenType,
                        "expires_in" to this.expiresIn(),
                        "refresh_token" to this.refreshToken?.refreshToken
                )
        }
}

[xhanin]

Sounds great, if identity replace username in AccessToken, Identity is extensible and you allow to customize the TokenResponse then it's perfect!

[adhesivee]

Fixed with 0.5.0