dnfdaemon: D-Bus API to reset the goal

With this patch the user can re-use the session to resolve multiple
transactions without running them. The use case might be to check what
dependencies would be installed with given package.

dnf5daemon-server/dbus/interfaces/org.rpm.dnf.v0.Goal.xml

@@ -106,6 +106,13 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
         <arg name="error_msg" type="s" />
     </method>
 
+    <!--
+        reset:
+        Reset the prepared rpm transaction. After this call the session is ready to perform another rpm transaction.
+    -->
+    <method name="reset">
+    </method>
+
 </interface>
 
 </node>

dnf5daemon-server/services/goal/goal.cpp

@@ -114,6 +114,10 @@ void Goal::dbus_register() {
         [this](sdbus::MethodCall call) -> void {
             session.get_threads_manager().handle_method(*this, &Goal::cancel, call, session.session_locale);
         });
+    dbus_object->registerMethod(
+        dnfdaemon::INTERFACE_GOAL, "reset", "", {}, "", {}, [this](sdbus::MethodCall call) -> void {
+            session.get_threads_manager().handle_method(*this, &Goal::reset, call, session.session_locale);
+        });
 }
 
 sdbus::MethodReply Goal::resolve(sdbus::MethodCall & call) {
@@ -349,3 +353,9 @@ sdbus::MethodReply Goal::cancel(sdbus::MethodCall & call) {
     reply << error_msg;
     return reply;
 }
+
+sdbus::MethodReply Goal::reset(sdbus::MethodCall & call) {
+    session.reset_goal();
+    auto reply = call.createReply();
+    return reply;
+}

dnf5daemon-server/services/goal/goal.hpp

@@ -37,6 +37,7 @@ class Goal : public IDbusSessionService {
     sdbus::MethodReply get_transaction_problems(sdbus::MethodCall & call);
     sdbus::MethodReply do_transaction(sdbus::MethodCall & call);
     sdbus::MethodReply cancel(sdbus::MethodCall & call);
+    sdbus::MethodReply reset(sdbus::MethodCall & call);
 };
 
 #endif