Add health check at /status

There are times where it would be good to monitor that osbuild-composer
is up and running. Add a very simple status check that always returns
200/OK. This can be expanded later to verify that other parts of
osbuild-composer are working properly.

Signed-off-by: Major Hayden <major@redhat.com>

internal/worker/server_test.go

@@ -14,6 +14,12 @@ import (
 	"github.com/osbuild/osbuild-composer/internal/worker"
 )
 
+// Ensure that the status request returns OK.
+func TestStatus(t *testing.T) {
+	server := worker.NewServer(nil, testjobqueue.New(), "")
+	test.TestRoute(t, server, false, "GET", "/status", ``, http.StatusOK, `{"status":"OK"}`, "message")
+}
+
 func TestErrors(t *testing.T) {
 	var cases = []struct {
 		Method         string