Make the endpoints configurable

[notdanilo]

We want to make it possible to have all the exchanges API endpoints configurable with default values in case the config value isn't present.

All the endpoints are hardcoded, and if they change for any reason, we would need to provide a new version of the API with the new endpoint.

It happened when Coinbase updated their endpoint from https://api.coinbase.com to https://api.pro.coinbase.com