refactor: move agent files to adapters for consistency

Signed-off-by: Deluan <deluan@navidrome.org>

adapters/spotify/responses.go

@@ -0,0 +1,30 @@
+package spotify
+
+type SearchResults struct {
+	Artists ArtistsResult `json:"artists"`
+}
+
+type ArtistsResult struct {
+	HRef  string   `json:"href"`
+	Items []Artist `json:"items"`
+}
+
+type Artist struct {
+	Genres     []string `json:"genres"`
+	HRef       string   `json:"href"`
+	ID         string   `json:"id"`
+	Popularity int      `json:"popularity"`
+	Images     []Image  `json:"images"`
+	Name       string   `json:"name"`
+}
+
+type Image struct {
+	URL    string `json:"url"`
+	Width  int    `json:"width"`
+	Height int    `json:"height"`
+}
+
+type Error struct {
+	Code    string `json:"error"`
+	Message string `json:"error_description"`
+}