Improved avatar background job

jobs/avatars/AvatarSource.go

@@ -0,0 +1,10 @@
+package main
+
+import (
+	"github.com/animenotifier/arn"
+)
+
+// AvatarSource describes a source where we can find avatar images for a user.
+type AvatarSource interface {
+	GetAvatar(*arn.User) *Avatar
+}