properly parse notes array on folder collections (#1)

Co-authored-by: David Ashby <delta.mu.alpha@gmail.com>
Reviewed-on: #1

discogs.go

@@ -105,6 +105,8 @@ func request(path string, params url.Values, resp interface{}) error {
 		switch response.StatusCode {
 		case http.StatusUnauthorized:
 			return ErrUnauthorized
+		case http.StatusTooManyRequests:
+			return ErrTooManyRequests
 		default:
 			return fmt.Errorf("unknown error: %s", response.Status)
 		}

errors.go

@@ -16,10 +16,11 @@ func (e *Error) Error() string {
 
 // APIErrors
 var (
-	ErrUnauthorized         = &Error{"authentication required"}
 	ErrCurrencyNotSupported = &Error{"currency does not supported"}
-	ErrUserAgentInvalid     = &Error{"invalid user-agent"}
 	ErrInvalidReleaseID     = &Error{"invalid release id"}
 	ErrInvalidSortKey       = &Error{"invalid sort key"}
 	ErrInvalidUsername      = &Error{"invalid username"}
+	ErrTooManyRequests      = &Error{"too many requests"}
+	ErrUnauthorized         = &Error{"authentication required"}
+	ErrUserAgentInvalid     = &Error{"invalid user-agent"}
 )

user_collection.go

@@ -67,7 +67,7 @@ type CollectionItemSource struct {
 	DateAdded        string           `json:"date_added"`
 	FolderID         int              `json:"folder_id,omitempty"`
 	InstanceID       int              `json:"instance_id"`
-	Notes            string           `json:"notes,omitempty"`
+	Notes            []Note           `json:"notes,omitempty"`
 	Rating           int              `json:"rating"`
 }
 
@@ -88,6 +88,12 @@ type BasicInformation struct {
 	Year        int            `json:"year"`
 }
 
+// Note ...
+type Note struct {
+	ID    int    `json:"field_id"`
+	Value string `json:"value"`
+}
+
 // CollectionItems list of items in a user’s collection
 type CollectionItems struct {
 	Pagination Page                   `json:"pagination"`