Implement assignment import and clear of budget

postgres/models.go

@@ -15,6 +15,14 @@ type Account struct {
 	Name     string
 }
 
+type Assignment struct {
+	ID         uuid.UUID
+	CategoryID uuid.UUID
+	Date       time.Time
+	Memo       sql.NullString
+	Amount     Numeric
+}
+
 type Budget struct {
 	ID               uuid.UUID
 	Name             string