Unimplemented Text Decoding Types in `PostgresTextDecoder`

[osaxma]

I think at some point we need to implement the rest of the types here:

postgresql-dart/lib/src/text_codec.dart

Lines 221 to 254 in 18b22c5

	class PostgresTextDecoder<T extends Object> extends Converter<Uint8List?, T?> {
	final PgDataType<T> _dataType;
	const PostgresTextDecoder(this._dataType);
	@override
	T? convert(Uint8List? input) {
	if (input == null) return null;
	final asText = utf8.decode(input);
	// ignore: unnecessary_cast
	switch (_dataType as PgDataType<Object>) {
	case PgDataType.text:
	return asText as T;
	case PgDataType.integer:
	case PgDataType.smallInteger:
	case PgDataType.bigInteger:
	case PgDataType.serial:
	case PgDataType.bigSerial:
	return int.parse(asText) as T;
	case PgDataType.real:
	case PgDataType.double:
	return num.parse(asText) as T;
	case PgDataType.boolean:
	return (asText == 'true') as T;
	// We could list out all cases, but it's about 20 lines of code.
	// ignore: no_default_cases
	default:
	throw UnimplementedError('Text decoding for $_dataType');
	}
	}
	}

Also:
I caught this incorrect decoding by coincidence when testing. Like in psql, in text data format (such in the simple protocol), true and false are returned as t and f, respectively.

postgresql-dart/lib/src/text_codec.dart

Lines 245 to 246 in 18b22c5

	case PgDataType.boolean:
	return (asText == 'true') as T;

Though, I am not sure if other valid boolean representation are possible (e.g. for true: 1, y, yes, on.. etc) to appear here.

I will push a small fix for this one in #118