GH-4071 Heavily refactor and rearchitect account system

This makes the account system much more modular
and makes it treat errors as something recoverable,
unless they come directly from the MSA refresh token
becoming invalid.

launcher/minecraft/auth/steps/XboxUserStep.cpp

@@ -0,0 +1,68 @@
+#include "XboxUserStep.h"
+
+#include <QNetworkRequest>
+
+#include "minecraft/auth/AuthRequest.h"
+#include "minecraft/auth/Parsers.h"
+
+XboxUserStep::XboxUserStep(AccountData* data) : AuthStep(data) {
+
+}
+
+XboxUserStep::~XboxUserStep() noexcept = default;
+
+QString XboxUserStep::describe() {
+    return tr("Logging in as an Xbox user.");
+}
+
+
+void XboxUserStep::rehydrate() {
+    // NOOP, for now. We only save bools and there's nothing to check.
+}
+
+void XboxUserStep::perform() {
+    QString xbox_auth_template = R"XXX(
+{
+    "Properties": {
+        "AuthMethod": "RPS",
+        "SiteName": "user.auth.xboxlive.com",
+        "RpsTicket": "d=%1"
+    },
+    "RelyingParty": "http://auth.xboxlive.com",
+    "TokenType": "JWT"
+}
+)XXX";
+    auto xbox_auth_data = xbox_auth_template.arg(m_data->msaToken.token);
+
+    QNetworkRequest request = QNetworkRequest(QUrl("https://user.auth.xboxlive.com/user/authenticate"));
+    request.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");
+    request.setRawHeader("Accept", "application/json");
+    auto *requestor = new AuthRequest(this);
+    connect(requestor, &AuthRequest::finished, this, &XboxUserStep::onRequestDone);
+    requestor->post(request, xbox_auth_data.toUtf8());
+    qDebug() << "First layer of XBox auth ... commencing.";
+}
+
+void XboxUserStep::onRequestDone(
+    QNetworkReply::NetworkError error,
+    QByteArray data,
+    QList<QNetworkReply::RawHeaderPair> headers
+) {
+    auto requestor = qobject_cast<AuthRequest *>(QObject::sender());
+    requestor->deleteLater();
+
+    if (error != QNetworkReply::NoError) {
+        qWarning() << "Reply error:" << error;
+        emit finished(AccountTaskState::STATE_FAILED_SOFT, tr("XBox user authentication failed."));
+        return;
+    }
+
+    Katabasis::Token temp;
+    if(!Parsers::parseXTokenResponse(data, temp, "UToken")) {
+        qWarning() << "Could not parse user authentication response...";
+        emit finished(AccountTaskState::STATE_FAILED_SOFT, tr("XBox user authentication response could not be understood."));
+        return;
+    }
+    m_data->userToken = temp;
+    emit finished(AccountTaskState::STATE_WORKING, tr("Got Xbox user token"));
+}