Serialize data as JSON with Accept: application/json

Similar to NixOS#607. According to the Catalyst[1] docs it's possible to
specify a data structure that is supposed to be serialized when
requesting i.e. a JSON response.

[1] https://metacpan.org/pod/Catalyst::Controller::REST#status_ok

src/lib/Hydra/Controller/Root.pm

@@ -197,6 +197,7 @@ sub machines :Local Args(0) {
         "where busy != 0 order by machine, stepnr",
         { Slice => {} });
     $c->stash->{template} = 'machine-status.tt';
+    $self->status_ok($c, entity => $c->stash->{machines});
 }
 
 
@@ -344,7 +345,9 @@ sub evals :Local Args(0) {
     $c->stash->{page} = $page;
     $c->stash->{resultsPerPage} = $resultsPerPage;
     $c->stash->{total} = $evals->search({hasnewbuilds => 1})->count;
-    $c->stash->{evals} = getEvals($self, $c, $evals, ($page - 1) * $resultsPerPage, $resultsPerPage)
+    $c->stash->{evals} = getEvals($self, $c, $evals, ($page - 1) * $resultsPerPage, $resultsPerPage);
+
+    $self->status_ok($c, entity => $c->stash->{evals});
 }