Any chance of exposing the 'source' parameter of the underlying service?

[torfason]

I need to access exact exchange rates according to the ECB. The underlying service that priceR uses allows this, with a single source parameter. For the latest rates, this would be:

• https://api.exchangerate.host/latest?base=eur (default)
• https://api.exchangerate.host/latest?base=eur&source=ecb (uses ECB as the source, and differs from the default for a number of currencies)

However, choosing the source or other parameters does not seem to be exposed by the priceR package – is that a feature you would consider adding at some point?