chore: remove entity index again

chore: add migration note

migrations/20220313_index_generation_hint.go

@@ -0,0 +1,24 @@
+package migrations
+
+import (
+	"github.com/emvi/logbuch"
+	"github.com/muety/wakapi/config"
+	"gorm.io/gorm"
+)
+
+func init() {
+	const name = "20220313-index_generation_hint"
+	f := migrationFunc{
+		name: name,
+		f: func(db *gorm.DB, cfg *config.Config) error {
+			if hasRun(name, db) {
+				return nil
+			}
+			logbuch.Info("please note: the following migrations might take a few minutes, as column types are changed and new indexes are created, have some patience")
+			setHasRun(name, db)
+			return nil
+		},
+	}
+
+	registerPreMigration(f)
+}