custom type unable to encode in pgx v5

```
type Time time.Time

type Type interface {
fmt.Stringer
json.Marshaler
json.Unmarshaler
sql.Scanner
driver.Valuer
schema.GormDataTypeInterface
}

// Implemented these interfaces
var _ Type = (*Time)(nil)
...
```

unable to encode Time{wall:0x0, ext:0, loc:(*time.Location)(nil)} into binary format for timestamp (OID 1114): cannot find encode plan

Start by reproducing the reported failure with the shown Time type and inspect pgx v5's timestamp encoding path for OID 1114. Determine whether the custom type should be supported through its implemented interfaces; done means a focused regression test passes or the limitation and required usage are documented.

Written by the indexing model from the issue text.