Stash rating system (#2830)

* add rating100 fields to represent rating range 1-100
* deprecate existing (1-5) rating fields
* add half- and quarter-star options for rating system
* add decimal rating system option

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

internal/api/changeset_translator.go

@@ -189,6 +189,36 @@ func (t changesetTranslator) nullInt64(value *int, field string) *sql.NullInt64
 	return ret
 }
 
+func (t changesetTranslator) ratingConversion(legacyValue *int, rating100Value *int) *sql.NullInt64 {
+	const (
+		legacyField    = "rating"
+		rating100Field = "rating100"
+	)
+
+	legacyRating := t.nullInt64(legacyValue, legacyField)
+	if legacyRating != nil {
+		if legacyRating.Valid {
+			legacyRating.Int64 = int64(models.Rating5To100(int(legacyRating.Int64)))
+		}
+		return legacyRating
+	}
+	return t.nullInt64(rating100Value, rating100Field)
+}
+
+func (t changesetTranslator) ratingConversionOptional(legacyValue *int, rating100Value *int) models.OptionalInt {
+	const (
+		legacyField    = "rating"
+		rating100Field = "rating100"
+	)
+
+	legacyRating := t.optionalInt(legacyValue, legacyField)
+	if legacyRating.Set && !(legacyRating.Null) {
+		legacyRating.Value = int(models.Rating5To100(int(legacyRating.Value)))
+		return legacyRating
+	}
+	return t.optionalInt(rating100Value, rating100Field)
+}
+
 func (t changesetTranslator) optionalInt(value *int, field string) models.OptionalInt {
 	if !t.hasField(field) {
 		return models.OptionalInt{}