message: Monitoring: User user's username as default silence creator value
  When creating a new silence, automatically fill the "Creator" field with
  the user's username.
diff: @@ -1459,14 +1459,18 @@ const EditSilence = connect(silenceParamToProps)(({ loaded, loadError, silence }
  );
  });
  -const CreateSilence = () => {
  +const CreateSilence_ = ({ createdBy }) => {
  const matchers = _.map(getURLSearchParams(), (value, name) => ({ name, value, isRegex: false }));
  return _.isEmpty(matchers) ? (
  - <SilenceForm saveButtonText="Create" title="Create Silence" />
  + <SilenceForm defaults={{ createdBy }} saveButtonText="Create" title="Create Silence" />
  ) : (
  - <SilenceForm defaults={{ matchers }} saveButtonText="Create" title="Silence Alert" />
  + <SilenceForm defaults={{ createdBy, matchers }} saveButtonText="Create" title="Silence Alert" />
  );
  };
  +const createSilenceStateToProps = ({ UI }: RootState) => ({
  + createdBy: UI.get('user')?.metadata?.name,
  +});
  +const CreateSilence = connect(createSilenceStateToProps)(CreateSilence_);
  const AlertmanagerYAML = () => {
  return (
  