plugins: metadata_importer: append rather that replace path in requests

This avoids problems when the api is hosted under a base path,
which would otherwise always be stripped.

eddy/plugins/metadata-importer/metadata_importer/widgets.py

@@ -307,7 +307,7 @@ def onRepositoryChanged(self, index):
         if repo:
             self.settings.setValue('metadata/index', self.combobox.currentIndex())
             url = QtCore.QUrl(repo.uri)
-            url.setPath('/classes')
+            url.setPath(f'{url.path()}/classes')
             request = QtNetwork.QNetworkRequest(url)
             request.setAttribute(MetadataRequest.RepositoryAttribute, repo)
             reply = self.session.nmanager.get(request)