refactor: a shorter name for converting leaf values to string

Change-Id: I175e86967bc7480f49623f381f7a3723f421bf89
diff --git a/src/system/Firmware.cpp b/src/system/Firmware.cpp
index 4b5956c..b1808e4 100644
--- a/src/system/Firmware.cpp
+++ b/src/system/Firmware.cpp
@@ -82,7 +82,7 @@
         auto lock = updateSlotStatus();
 
         try {
-            auto source = utils::getValueAsString(*input.findPath("url"));
+            auto source = utils::asString(*input.findPath("url"));
             m_rauc->install(source);
         } catch (sdbus::Error& e) {
             m_log->warn("RAUC install error: '{}'", e.what());
@@ -95,7 +95,7 @@
     m_srSubscribeRPC = m_srSessionRPC.onRPCAction(CZECHLIGHT_SYSTEM_FIRMWARE_MODULE_PREFIX + "installation/install", cbRPC);
 
     ::sysrepo::RpcActionCb markSlotAs = [this](auto, auto, auto path, auto input, auto, auto, auto) {
-        auto bootName = utils::getValueAsString(*input.parent()->findPath("name"));
+        auto bootName = utils::asString(*input.parent()->findPath("name"));
         std::string action;
         if (path == CZECHLIGHT_SYSTEM_FIRMWARE_MODULE_PREFIX + "firmware-slot/set-active-after-reboot") {
             action = "active";