Add simple cache warmer, disabled by default

db/migration/20201025222059_purge_cache.go

@@ -0,0 +1,25 @@
+package migration
+
+import (
+	"database/sql"
+	"os"
+	"path/filepath"
+
+	"github.com/deluan/navidrome/conf"
+	"github.com/pressly/goose"
+)
+
+func init() {
+	goose.AddMigration(Up20201025222059, Down20201025222059)
+}
+
+func Up20201025222059(tx *sql.Tx) error {
+	cacheFolder := filepath.Join(conf.Server.DataFolder, "cache")
+	notice(tx, "Purging all cache entries, as the format of the cache changed.")
+	return os.RemoveAll(cacheFolder)
+}
+
+func Down20201025222059(tx *sql.Tx) error {
+	// This code is executed when the migration is rolled back.
+	return nil
+}