add github.com/jackc/pgtype import if there are enums using pgx/v4

Author: toqueteos

internal/codegen/golang/imports.go

@@ -262,6 +262,11 @@ func (i *importer) modelImports() fileImports {
 	if len(i.Enums) > 0 {
 		std["fmt"] = struct{}{}
 		std["database/sql/driver"] = struct{}{}
+
+		sqlpkg := parseDriver(i.Settings.Go.SqlPackage)
+		if sqlpkg.Package() == "pgx/v4" {
+			pkg[ImportSpec{Path: "github.com/jackc/pgtype"}] = struct{}{}
+		}
 	}
 
 	return sortedImports(std, pkg)