Add support for `decimal.Decimal`

[scnerd]

ormsgpack version: 1.2.3

Current behavior

>>> import decimal
>>> ormsgpack.packb(decimal.Decimal("12.345"))
Traceback (most recent call last):
  File "...", in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-119-58a3aa663d1a>", line 1, in <module>
    ormsgpack.packb(decimal.Decimal("12.345"))
TypeError: Type is not msgpack serializable: decimal.Decimal

Desired behavior

Decimals seem to be primarily stored as strings. It should be lossless and reasonably fast to cast decimal.Decimal to str during serialization, and back during deserialization.

[aviramha]

hey @scnerd, thanks for the suggestion. I don't have time to add more features currently, but if someone wants to send a PR it'd be great!

[Weezytoughtem]

Decimals seem to be primarily stored as strings. It should be lossless and reasonably fast to cast decimal.Decimal to str during serialization, and back during deserialization.

[exg]

Arbitrary types can be serialized using the default callable, see https://github.com/aviramha/ormsgpack#default (the example uses decimal).