Internal Server Error when requested conversion amount is too small

[sc4l3r]

When I request a conversion with an amount which, because of the conversion rate, would result in a converted amount of less than 1n, an Internal Server Error is returned.

In the server logs I see:

[<NO_REQUEST_ID>] DEBUG Calculating exchange rate for BTC -> USD:
[<NO_REQUEST_ID>] DEBUG Base rate: 125341.55998122648:
[<NO_REQUEST_ID>] DEBUG Converted:: 0n
[<NO_REQUEST_ID>] ERROR KeetaAnchorHTTP.Server: Error: Invalid converted amount
    at Object.getConversionRateAndFee (/workspace/demo-fx-anchor/apps/api/src/app.ts:44:11)

Expected Behavior

A Bad Request response is returned with a message that indicates what I did wrong, e.g. "Requested amount is too small".

Steps to reproduce

1. Start the anchor (or use the one deployed at https://demo-fx-anchor.test.keeta.com).

2. Request a conversion of 1n BTC (0.00000001) to USD:

   curl 'http://localhost:8080/api/getEstimate' \
     -X POST -H 'Content-Type: application/json' -H 'Accept: application/json' \
     --data-raw '{"request":{"from":"keeta_ao47xyunmfh5jcdkm7mgrfaaddp7a2nt2xvwrph6cgurvbeixh77qkfsglgms","to":"keeta_ap7wtjtyfc4yvt26jstau4n76uqnv4znjnz5pcgpnjsty5vjbxkvmk55yl4f6","amount":"0x1","affinity":"from"}}'

3. Observe the response {"ok":false,"error":"Internal Server Error"}.