test(registry): add unit tests for registry behavior

internal/registry/registry.go

@@ -111,9 +111,6 @@ func (r *registry) Update(user string, oldKey, newKey Key) error {
 	client.Slug().Set(newKey.Id)
 	r.slugIndex[newKey] = user
 
-	if r.byUser[user] == nil {
-		r.byUser[user] = make(map[Key]Session)
-	}
 	r.byUser[user][newKey] = client
 	return nil
 }