How can we detect if a number is an integral value?

[MangelMaxime]

There is currently a subtle bug in Thoth.Json (since for ever probably), where number with decimal set to 0 like 10.0 or 2120.0 are considered integral value.

This is because in JavaScript the test we use is:

function isIntegral(value) {
    return isFinite(value) && Math.floor(value) === value;
}

// Returns
isIntegral(10.0) // ❌
isIntegral(2120.0) // ❌
isIntegral(10.1) // ✅

Case marked with ❌ are incorrect because they return true instead of false.

This means that 10.0 is consider a valid number for int16, etc.

This bug is not present in Thoth.Json.Newtonsoft, neither in Thoth.Json.Python.