feat(motd): add the ability to display motd and dimiss information panels (#2191)

* feat(api): add motd handler

* feat(app): add the motd api layer

* feat(motd): display motd and add the ability to dismiss information messages

* style(home): relocate important message before info01

* feat(api): silently fail when an error occurs during motd retrieval

api/http/client/client.go

@@ -13,6 +13,10 @@ import (
 	"github.com/portainer/portainer"
 )
 
+const (
+	errInvalidResponseStatus = portainer.Error("Invalid response status (expecting 200)")
+)
+
 // HTTPClient represents a client to send HTTP requests.
 type HTTPClient struct {
 	*http.Client
@@ -75,6 +79,10 @@ func Get(url string) ([]byte, error) {
 	}
 	defer response.Body.Close()
 
+	if response.StatusCode != http.StatusOK {
+		return nil, errInvalidResponseStatus
+	}
+
 	body, err := ioutil.ReadAll(response.Body)
 	if err != nil {
 		return nil, err