GODT-1553: RPC definition and mocks

WIP: updates

WIP: cache on disk and autostart.

WIP: mail, keychain and more.

WIP: updated grpc version in go mod file.

WIP: user list.

WIP: RPC service placeholder

WIP: test C++ RPC client skeleton.

Other: missing license script update.

WIP: use Qt test framework.

WIP: test for app and login calls.

WIP: test for update & cache on disk calls.

WIP: tests for mail settings calls.

WIP: all client tests.

WIP: linter fixes.

WIP: fix missing license link.

WIP: update dependency_license script for gRPC and protobuf.

WIP: removed unused file.

WIP: app & login event streaming tests.

WIP: update event stream tests.

WIP: completed event streaming tests.

test/rpc/client/Exception.h

@@ -0,0 +1,44 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+#ifndef BRIDGE_RPC_CLIENT_TEST_EXCEPTION_H
+#define BRIDGE_RPC_CLIENT_TEST_EXCEPTION_H
+
+
+#include <QtCore>
+#include <stdexcept>
+
+//**********************************************************************************************************************
+/// \brief Exception class
+//**********************************************************************************************************************
+class Exception: public std::exception
+{
+public: // member functions
+    explicit Exception(QString what = QString()) noexcept; ///< Constructor
+    Exception(Exception const& ref) noexcept; ///< copy constructor
+    Exception(Exception&& ref) noexcept; ///< copy constructor
+    Exception& operator=(Exception const&) = delete; ///< Disabled assignment operator
+    Exception& operator=(Exception&&) = delete; ///< Disabled assignment operator
+    ~Exception() noexcept = default; ///< Destructor
+    QString const& qwhat() const noexcept; ///< Return the description of the exception as a QString
+    const char* what() const noexcept override; ///< Return the description of the exception as C style string
+
+private: // data members
+    QString const what_; ///< The description of the exception
+};
+
+#endif //BRIDGE_RPC_CLIENT_TEST_EXCEPTION_H