BigInteger JSON serialization should be string if their value is bigger than 2^53

[AlexandreBossard]

BigInteger serialization does not respect the JSON specification when value is above 2^53

Expected Behavior

The serialized json value should be of type string, and not number, when value is above the 2^53.

Current Behavior

The value is serialized as number json, which is not guaranteed to be interoperable across json implementation. For example Hardhat refuses it.

Possible Solution

Declaring the C# type as string instead of BigInteger works, at least for Hardhat.

Steps to Reproduce

(coming soon)

Context (Environment)

.Net7 Core on linux + Hardhat 2.17.3 + Nethereum 4.17.1

Detailed Description

Using the EIP2612 Permit model and assigning the deadline field to the max uint256 value 115792089237316195423570985008687907853269984665640564039457584007913129639935 will make Hardhat's eth_signTypedData_v4 call assert.

Possible Implementation

I believe the bug is somewhere around:

Nethereum/src/Nethereum.ABI/EIP712/TypedDataRawJsonConversion.cs

Line 196 in 49a0c1a

private static List<JProperty> GetJProperties(string mainTypeName, MemberValue[] values, TypedDataRaw typedDataRaw)

It should not insert the BigInteger value as is, but check for maximum (and minimum) value and serialize it to string.