Add return type for artist/album lookup endpoint

Closes #5282

src/Lidarr.Api.V1/Albums/AlbumLookupController.cs

@@ -20,7 +20,8 @@ namespace Lidarr.Api.V1.Albums
         }
 
         [HttpGet]
-        public object Search(string term)
+        [Produces("application/json")]
+        public IEnumerable<AlbumResource> Search(string term)
         {
             var searchResults = _searchProxy.SearchForNewAlbum(term, null);
             return MapToResource(searchResults).ToList();

src/Lidarr.Api.V1/Artist/ArtistLookupController.cs

@@ -23,7 +23,8 @@ namespace Lidarr.Api.V1.Artist
         }
 
         [HttpGet]
-        public object Search([FromQuery] string term)
+        [Produces("application/json")]
+        public IEnumerable<ArtistResource> Search([FromQuery] string term)
         {
             var searchResults = _searchProxy.SearchForNewArtist(term);
             return MapToResource(searchResults).ToList();

src/Lidarr.Api.V1/Search/SearchController.cs

@@ -24,7 +24,8 @@ namespace Lidarr.Api.V1.Search
         }
 
         [HttpGet]
-        public object Search([FromQuery] string term)
+        [Produces("application/json")]
+        public IEnumerable<SearchResource> Search([FromQuery] string term)
         {
             var searchResults = _searchProxy.SearchForNewEntity(term);
             return MapToResource(searchResults).ToList();