We don't recommend using this provider.
The Namecheap API is very crappy and requires that we update EVERY dns record to just modify a single record.
It is also currently limited to domains that have no more than 10 A records. This could be fixed by changing the request from a HTTP GET to a POST but unfortunately Namecheap hasn't documented the POST method.
If you are using docker-compose or creating your own container then you need to set the following environment variable when you are creating the container.
AUTH_PROVIDER_TOKEN=name cheap Api Key
AUTH_PROVIDER_USERNAME=name cheap username