@JvmOverloads fun issueAccessToken(authCode: String, redirectUri: String = "kakao${KakaoSdk.applicationContextInfo.clientId}://oauth", clientId: String = KakaoSdk.applicationContextInfo.clientId, approvalType: String = "individual", androidKeyHash: String = KakaoSdk.applicationContextInfo.signingKeyHash): Single<AccessTokenResponse>
RxAuthCodeClient 를 이용하여 발급 받은 authorization code 를 사용하여 액세스 토큰을 발급한다.
Return
Single instance that will emit AccessTokenResponse.