Fix/preserve original error in translate

[JonathanGunawan30]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

Previously, Translate() discarded the original *pgconn.PgError and returned
only the sentinel error (e.g. gorm.ErrDuplicatedKey), breaking the error chain.

This fix wraps both errors using fmt.Errorf with multiple %w verbs (Go 1.20+),
so callers can still use errors.Is() for gorm error checking while also being
able to unwrap the original *pgconn.PgError via errors.As() to access details
like Detail, ConstraintName, etc.

User Case Description

Fixes #332

Before this fix:

errors.Is(err, gorm.ErrDuplicatedKey) // ✅ true
errors.As(err, &pgErr)                // ❌ false — original pgError is lost
pgErr.Detail                          // ❌ inaccessible

After this fix:

errors.Is(err, gorm.ErrDuplicatedKey) // ✅ true
errors.As(err, &pgErr)                // ✅ true
pgErr.Detail                          // ✅ "Key (email)=(foo@bar.com) already exists."
pgErr.ConstraintName                  // ✅ "users_email_key"