lint(errorlint): handle wrapped errors

Enable errorlint and preserve wrapped error chains so runtime checks
and tests classify failures correctly. This also makes Route53
surface insert failures instead of silently dropping them.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

plugin/transfer/transfer.go

@@ -94,7 +94,7 @@ func (t *Transfer) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Ms
 	var err error
 	for _, p := range t.Transferers {
 		pchan, err = p.Transfer(state.Name(), serial)
-		if err == ErrNotAuthoritative {
+		if errors.Is(err, ErrNotAuthoritative) {
 			// plugin was not authoritative for the zone, try next plugin
 			continue
 		}