msgpack: add string() for decimal

Added a decimal type conversion function to a string, added tests for this function. Fixed name of function.

Added #322

Author: babyTsakhes

decimal/decimal.go

@@ -156,7 +156,7 @@ func decimalDecoder(d *msgpack.Decoder, v reflect.Value, extLen int) error {
 // For the general case, use shopspring/decimal.String().
 // For cases where it is known that numbers contain less than 26 characters,
 // you can use the optimized version.
-func (d Decimal) String() string {
+func (d Decimal) StringOptimized() string {
 	coefficient := d.Decimal.Coefficient() // Note: In shopspring/decimal, the number is stored as coefficient *10^exponent, where exponent can be negative.
 	exponent := d.Decimal.Exponent()
 

decimal/decimal_test.go

@@ -770,7 +770,7 @@ func TestDecimalStringOptimized(t *testing.T) {
 			dec, err := MakeDecimalFromString(tt.input)
 			assert.NoError(t, err)
 
-			result := dec.String()
+			result := dec.StringOptimized()
 
 			assert.Equal(t, tt.expected, result)
 
@@ -802,8 +802,8 @@ func TestTarantoolBCDCompatibility(t *testing.T) {
 			err = dec2.UnmarshalMsgpack(msgpackData)
 			assert.NoError(t, err)
 
-			originalStr := dec.String()
-			roundtripStr := dec2.String()
+			originalStr := dec.StringOptimized()
+			roundtripStr := dec2.StringOptimized()
 
 			assert.Equal(t, originalStr, roundtripStr,
 				"BCD roundtrip failed for input: %s", input)