Call to Auth0 API to get new Access Token based on existing refresh token

Auth0.renewAuth(refreshToken)

class SessionHelper private constructor() {

...

    fun refreshCredentials(): String? {

        val refreshToken = refreshToken
        if (refreshToken != null) {
            val account = Auth0(String.from(R.string.AUTH0_API_ID), String.from(R.string.AUTH0_API_DOMAIN))
            val authentication = AuthenticationAPIClient(account)

            val response = authentication.renewAuth(refreshToken).execute()
            response.idToken?.let { saveUserCredentials(accessToken = it) }

            return response.idToken

        } else return null
    }

    fun saveUserCredentials(accessToken: String, userEmail: String? = null) {
        this.accessToken = accessToken
        this.userEmail = userEmail
        val shared = MyApp.sharedPreferences ?: return
        val editor = shared.edit()
        editor.putString(Constants.SharedConfig.accessToken, this.accessToken)
        userEmail?.let { editor.putString(Constants.SharedConfig.userEmail, this.userEmail) }
        editor.apply()
    }
}