json.Marshal with `omitzero` broken on decimal.Zero

Go v1.24 introduced the `iszero` tag: https://pkg.go.dev/encoding/json#Marshal >The "omitzero" option specifies that the field should be omitted from the encoding if the field has a zero value, according to rules: > >1) If the field type has an "IsZero() bool" method, that will be used to determine whether the value is zero. > >2) Otherwise, the value is zero if it is the zero value for its type. This works great for decimal.Decimal as it implements `IsZero`, however it breaks when using a nested struct containing `decimal.Zero`, as the struct now no longer is the zero value. See this example: https://go.dev/play/p/E5ZACVij_Rh My suggestion is to use `var Zero Decimal`, and to ensure it doesn't need to initialise when using calculations, we can implement this: ```go var zeroValue = new(big.Int) func (d *Decimal) getValue() *big.Int { if d.value == nil { return zeroValue } return d.value } ``` That way we never need to initialise a zero value `Decimal` for a calculation as they all use the same pointer.