QMP: QError: New QERR_UNSUPPORTED

New QERR_UNSUPPORTED for unsupported commands or requests.
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

qerror.c

@@ -200,6 +200,10 @@ static const QErrorStringTable qerror_table[] = {
         .error_fmt = QERR_UNDEFINED_ERROR,
         .desc      = "An undefined error has ocurred",
     },
+    {
+        .error_fmt = QERR_UNSUPPORTED,
+        .desc      = "this feature or command is not currently supported",
+    },
     {
         .error_fmt = QERR_UNKNOWN_BLOCK_FORMAT_FEATURE,
         .desc      = "'%(device)' uses a %(format) feature which is not "

qerror.h

@@ -165,6 +165,9 @@ QError *qobject_to_qerror(const QObject *obj);
 #define QERR_UNDEFINED_ERROR \
     "{ 'class': 'UndefinedError', 'data': {} }"
 
+#define QERR_UNSUPPORTED \
+    "{ 'class': 'Unsupported', 'data': {} }"
+
 #define QERR_UNKNOWN_BLOCK_FORMAT_FEATURE \
     "{ 'class': 'UnknownBlockFormatFeature', 'data': { 'device': %s, 'format': %s, 'feature': %s } }"