Retrieve FX details

curl --request POST \
  --url https://api.sand.getivy.de/api/service/fx/retrieve \
  --header 'Content-Type: application/json' \
  --header 'X-Ivy-Api-Key: <api-key>' \
  --data '{
  "fxId": "<string>"
}'

{
  "rate": "<string>",
  "targetAmount": "<string>",
  "sourceAmount": "<string>",
  "targetCurrency": "EUR",
  "sourceCurrency": "EUR"
}