Kleat doesn't fill in echo.yml's Spinnaker baseUrl

[achew22]

When Kleat generates the echo.yml file, it should additionally generate the field spinnaker.baseUrl which it might be okay to infer from security.uiSecurity.overrideBaseURL in the halconfig.

The result should be something like this in the head of echo.yml:

spinnaker:
  baseUrl: https://spinnaker.my.domain

For more context. Slack thread.

Thanks @nimakaviani and @kskewes for your help.