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/EntitlementsStep.cpp

@@ -0,0 +1,53 @@
+#include "EntitlementsStep.h"
+
+#include <QNetworkRequest>
+#include <QUuid>
+
+#include "minecraft/auth/AuthRequest.h"
+#include "minecraft/auth/Parsers.h"
+
+EntitlementsStep::EntitlementsStep(AccountData* data) : AuthStep(data) {}
+
+EntitlementsStep::~EntitlementsStep() noexcept = default;
+
+QString EntitlementsStep::describe() {
+    return tr("Determining game ownership.");
+}
+
+
+void EntitlementsStep::perform() {
+    auto uuid = QUuid::createUuid();
+    m_entitlementsRequestId = uuid.toString().remove('{').remove('}');
+    auto url = "https://api.minecraftservices.com/entitlements/license?requestId=" + m_entitlementsRequestId;
+    QNetworkRequest request = QNetworkRequest(url);
+    request.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");
+    request.setRawHeader("Accept", "application/json");
+    request.setRawHeader("Authorization", QString("Bearer %1").arg(m_data->yggdrasilToken.token).toUtf8());
+    AuthRequest *requestor = new AuthRequest(this);
+    connect(requestor, &AuthRequest::finished, this, &EntitlementsStep::onRequestDone);
+    requestor->get(request);
+    qDebug() << "Getting entitlements...";
+}
+
+void EntitlementsStep::rehydrate() {
+    // NOOP, for now. We only save bools and there's nothing to check.
+}
+
+void EntitlementsStep::onRequestDone(
+    QNetworkReply::NetworkError error,
+    QByteArray data,
+    QList<QNetworkReply::RawHeaderPair> headers
+) {
+    auto requestor = qobject_cast<AuthRequest *>(QObject::sender());
+    requestor->deleteLater();
+
+#ifndef NDEBUG
+    qDebug() << data;
+#endif
+
+    // TODO: check presence of same entitlementsRequestId?
+    // TODO: validate JWTs?
+    Parsers::parseMinecraftEntitlements(data, m_data->minecraftEntitlement);
+
+    emit finished(AccountTaskState::STATE_WORKING, tr("Got entitlements"));
+}