fix: add missing overspend mode when importing from YNAB4 (#470)

When importing from YNAB 4, we account for the different mode handling
of the overspend mode by setting the overspend mode to `AFFECT_ENVELOPE`
for all months up to and including the month when the import happens.

This PR fixes the handling so that it actually includes the `AFFECT_ENVELOPE` setting.

Author: morremeyer

pkg/importer/parser/ynab4/parse.go

@@ -458,6 +458,9 @@ func fixOverspendHandling(resources *types.ParsedResources) {
 						monthConfigs = append(monthConfigs, types.MonthConfig{
 							Model: models.MonthConfig{
 								Month: checkMonth,
+								MonthConfigCreate: models.MonthConfigCreate{
+									OverspendMode: models.AffectEnvelope,
+								},
 							},
 							Category: mConfig.Category,
 							Envelope: mConfig.Envelope,