Add support for string amounts

[bountin]

I'm consuming an API that serializes the amounts as string values and the current implementation fails at deserialization with a JsonMappingException (Current token (VALUE_STRING) not numeric, can not use numeric value accessors)

I thought it doesn't hurt to support this use case in the library and so here is my PR :)

The way via the context should not add much overhead performance wise as the BigIntegerDeserializer does more or less the same in the INT and FLOAT cases but also handles Strings correctly. The indirection just adds some more stack frames.

[AlexanderYastrebov]

@whiskeysierra

1. Should it be liberal to deserialize both types or there should be a deserialization feature enabled to support Strings? I would propose to act as Jackson core acts to follow least astonishment principle.
2. I think there should be an implementation+test and feature switch to serialize into String as well.

[whiskeysierra]

@bountin Thanks for the contribution!

Should it be liberal to deserialize both types or there should be a deserialization feature enabled to support Strings?

Jackson does it without configuration, by default? In that case I'd agree to do the same.

I think there should be an implementation+test and feature switch to serialize into String as well.

With Postel's Law in mind:

Be conservative in what you send, be liberal in what you accept.

I'd prefer not to support it, since it violates our schema for monetary values.

[AlexanderYastrebov]

@whiskeysierra

I'd prefer not to support it, since it violates our schema for monetary values.

If there is a system from which client reads Strings, I am sure there is (or will be) a system which will require Strings as input

[whiskeysierra]

I am sure there is (or will be) a system which will require Strings as input

That system will violate both, our schema as well as Postel's law. Let's wait for that to happen and add support for it, if and when needed.

[whiskeysierra]

👍

[whiskeysierra]

@bountin I released 0.12.0. Should be in central, soon.

[bountin]

Thanks for the fast merge & release 👍