Add ExternalInformation core service (not a great name, I know)

model/artist.go

@@ -26,6 +26,7 @@ type ArtistRepository interface {
 	Exists(id string) (bool, error)
 	Put(m *Artist) error
 	Get(id string) (*Artist, error)
+	FindByName(name string) (*Artist, error)
 	GetStarred(options ...QueryOptions) (Artists, error)
 	Search(q string, offset int, size int) (Artists, error)
 	Refresh(ids ...string) error

model/artist_info.go

@@ -0,0 +1,11 @@
+package model
+
+type ArtistInfo struct {
+	ID             string
+	Name           string
+	Bio            string
+	Similar        []Artist
+	SmallImageUrl  string
+	MediumImageUrl string
+	LargeImageUrl  string
+}