Introduce NeoChatConnection

Previously, some functions that conceptually belong to the connection needed to be in the Controller, since we didn't have a place to put them.
This fixes that by extending the Connection class in a similar way as we extend the Room class.

src/neochatconnection.h

@@ -0,0 +1,51 @@
+// SPDX-FileCopyrightText: 2023 Tobias Fella <tobias.fella@kde.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <QObject>
+
+#include <Quotient/connection.h>
+
+class NeoChatConnection : public Quotient::Connection
+{
+    Q_OBJECT
+
+    /**
+     * @brief The account label for this account.
+     *
+     * Account labels are a concept specific to NeoChat, allowing accounts to be
+     * labelled, e.g. for "Work", "Private", etc.
+     *
+     * Set to an empty string to remove the label.
+     */
+    Q_PROPERTY(QString label READ label WRITE setLabel NOTIFY labelChanged)
+
+public:
+    NeoChatConnection(QObject *parent = nullptr);
+    NeoChatConnection(const QUrl &server, QObject *parent = nullptr);
+
+    Q_INVOKABLE void logout(bool serverSideLogout);
+    Q_INVOKABLE QVariantList getSupportedRoomVersions() const;
+
+    /**
+     * @brief Change the password for an account.
+     *
+     * The function emits a passwordStatus signal with a PasswordStatus value when
+     * complete.
+     *
+     * @sa PasswordStatus, passwordStatus
+     */
+    Q_INVOKABLE void changePassword(const QString &currentPassword, const QString &newPassword);
+
+    /**
+     * @brief Change the avatar for an account.
+     */
+    Q_INVOKABLE bool setAvatar(const QUrl &avatarSource);
+
+    [[nodiscard]] QString label() const;
+    void setLabel(const QString &label);
+
+Q_SIGNALS:
+    void labelChanged();
+};