Keycloak service name is hard-coded in the API service

[smlx]

Describe the bug
The keycloak service name is hard-coded in the API client. This means that it cannot be set via environment variables in the usual 12-factor way.

To Reproduce
Steps to reproduce the behavior:

1. Name the keycloak service anything other than keycloak.
2. See error on api service startup.

Expected behavior
I expect that the default keycloak service name would be able to be overridden by environment variable.

Screenshots
n/a

Additional context
The keycloak service is hard-coded here:
https://github.com/amazeeio/lagoon/blob/master/services/api/src/clients/keycloakClient.js#L7