fix: avoid generating nested currency options map

[augustoccesar]

Summary

This PR adds a check to verify if the ty is already a CurrencyMap to avoid generating any nested Option<CurrencyMap<...>> as shown on #480 .

On a side note: this is something that will also be fixed on #452.

Closes #480
Closes #427

Checklist

• ran cargo make fmt
• using conventional commits to hightlight user-facing fixes and features

[arlyon]

Thanks! 🎉