feat: add beatport provider

internal/app/app_test.go

@@ -864,6 +864,41 @@ func TestBuildTagMetadataReplayGainFallbacks(t *testing.T) {
 	}
 }
 
+func TestBuildTagMetadataInitialKey(t *testing.T) {
+	meta := map[string]any{
+		"key":       "E Minor",
+		"album":     map[string]any{"title": "Album"},
+		"performer": map[string]any{"name": "Artist"},
+	}
+
+	tags := buildTagMetadata(meta, "Song", "beatport", "42", ripTrackOptions{})
+	if tags.InitialKey != "Em" {
+		t.Fatalf("InitialKey=%q", tags.InitialKey)
+	}
+}
+
+func TestNormalizeInitialKey(t *testing.T) {
+	tests := map[string]string{
+		"C Major":   "C",
+		"Db Major":  "Db",
+		"F# Major":  "F#",
+		"E Minor":   "Em",
+		"C# Minor":  "C#m",
+		"Bb Minor":  "Bbm",
+		"g# minor":  "G#m",
+		"F#m":       "F#m",
+		"Ab":        "Ab",
+		"Not A Key": "Not A Key",
+		"C# Major":  "C# Major",
+		"Db Minor":  "Db Minor",
+	}
+	for input, want := range tests {
+		if got := normalizeInitialKey(input); got != want {
+			t.Fatalf("normalizeInitialKey(%q)=%q want %q", input, got, want)
+		}
+	}
+}
+
 func TestBuildTagMetadataReplayGainFallsBackToDeezerGain(t *testing.T) {
 	meta := map[string]any{
 		"gain":      float64(-10),