Serialize binary bytea cols into hex/base64 (#537)

- Adds binary serialization into hex/base64
- Default codec is base64
- Codec can be changed via `--binary-codec` CLI option

pkg/client/codec_test.go

@@ -0,0 +1,49 @@
+package client
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSetBinaryCodec(t *testing.T) {
+	examples := []struct {
+		input string
+		err   error
+	}{
+		{input: CodecNone, err: nil},
+		{input: CodecBase64, err: nil},
+		{input: CodecHex, err: nil},
+		{input: "foobar", err: errors.New("invalid binary codec: foobar")},
+	}
+
+	for _, ex := range examples {
+		t.Run(ex.input, func(t *testing.T) {
+			val := BinaryCodec
+			defer func() {
+				BinaryCodec = val
+			}()
+
+			assert.Equal(t, ex.err, SetBinaryCodec(ex.input))
+		})
+	}
+}
+
+func Test_encodeBinaryData(t *testing.T) {
+	examples := []struct {
+		input    string
+		expected string
+		encoding string
+	}{
+		{input: "hello world", expected: "hello world", encoding: CodecNone},
+		{input: "hello world", expected: "aGVsbG8gd29ybGQ=", encoding: CodecBase64},
+		{input: "hello world", expected: "68656c6c6f20776f726c64", encoding: CodecHex},
+	}
+
+	for _, ex := range examples {
+		t.Run(ex.input, func(t *testing.T) {
+			assert.Equal(t, ex.expected, encodeBinaryData([]byte(ex.input), ex.encoding))
+		})
+	}
+}