feat: make Unicode handling in external API calls configurable (#4277)

* feat: make Unicode handling in external API calls configurable

- Add DevPreserveUnicodeInExternalCalls config option (default: false)
- Refactor external provider to use NameForExternal() method on auxArtist
- Remove redundant Name field from auxArtist struct
- Update all external API calls (image, URL, biography, similar, top songs, MBID) to use configurable Unicode handling
- Add comprehensive tests for both Unicode-preserving and normalized behaviors
- Refactor tests to use constants and improved structure with BeforeEach blocks

Fixes issue where Spotify integration failed to find artist images for artists with Unicode characters (e.g., en dash) in their names.

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

* address comments

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

* avoid calling str.Clean multiple times

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

* refactor: apply Unicode handling pattern to auxAlbum

Extended the configurable Unicode handling to album names, matching the
pattern already implemented for artist names. This ensures consistent behavior
when DevPreserveUnicodeInExternalCalls is enabled for both artist and album
external API calls.

Changes:
- Removed Name field from auxAlbum struct, added Name() method with Unicode logic
- Updated getAlbum, UpdateAlbumInfo, populateAlbumInfo, and AlbumImage functions
- Added comprehensive tests for album Unicode handling (preserve and normalize)
- Fixed typo in artist image test description

---------

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

conf/configuration.go

@@ -106,32 +106,33 @@ type configOptions struct {
 	Agents                          string
 
 	// DevFlags. These are used to enable/disable debugging and incomplete features
-	DevLogLevels                     map[string]string `json:",omitempty"`
-	DevLogSourceLine                 bool
-	DevEnableProfiler                bool
-	DevAutoCreateAdminPassword       string
-	DevAutoLoginUsername             string
-	DevActivityPanel                 bool
-	DevActivityPanelUpdateRate       time.Duration
-	DevSidebarPlaylists              bool
-	DevShowArtistPage                bool
-	DevUIShowConfig                  bool
-	DevNewEventStream                bool
-	DevOffsetOptimize                int
-	DevArtworkMaxRequests            int
-	DevArtworkThrottleBacklogLimit   int
-	DevArtworkThrottleBacklogTimeout time.Duration
-	DevArtistInfoTimeToLive          time.Duration
-	DevAlbumInfoTimeToLive           time.Duration
-	DevExternalScanner               bool
-	DevScannerThreads                uint
-	DevSelectiveWatcher              bool
-	DevInsightsInitialDelay          time.Duration
-	DevEnablePlayerInsights          bool
-	DevEnablePluginsInsights         bool
-	DevPluginCompilationTimeout      time.Duration
-	DevExternalArtistFetchMultiplier float64
-	DevOptimizeDB                    bool
+	DevLogLevels                      map[string]string `json:",omitempty"`
+	DevLogSourceLine                  bool
+	DevEnableProfiler                 bool
+	DevAutoCreateAdminPassword        string
+	DevAutoLoginUsername              string
+	DevActivityPanel                  bool
+	DevActivityPanelUpdateRate        time.Duration
+	DevSidebarPlaylists               bool
+	DevShowArtistPage                 bool
+	DevUIShowConfig                   bool
+	DevNewEventStream                 bool
+	DevOffsetOptimize                 int
+	DevArtworkMaxRequests             int
+	DevArtworkThrottleBacklogLimit    int
+	DevArtworkThrottleBacklogTimeout  time.Duration
+	DevArtistInfoTimeToLive           time.Duration
+	DevAlbumInfoTimeToLive            time.Duration
+	DevExternalScanner                bool
+	DevScannerThreads                 uint
+	DevSelectiveWatcher               bool
+	DevInsightsInitialDelay           time.Duration
+	DevEnablePlayerInsights           bool
+	DevEnablePluginsInsights          bool
+	DevPluginCompilationTimeout       time.Duration
+	DevExternalArtistFetchMultiplier  float64
+	DevOptimizeDB                     bool
+	DevPreserveUnicodeInExternalCalls bool
 }
 
 type scannerOptions struct {
@@ -630,6 +631,7 @@ func setViperDefaults() {
 	viper.SetDefault("devplugincompilationtimeout", time.Minute)
 	viper.SetDefault("devexternalartistfetchmultiplier", 1.5)
 	viper.SetDefault("devoptimizedb", true)
+	viper.SetDefault("devpreserveunicodeinexternalcalls", false)
 }
 
 func init() {