title: How to deal with multiple application config files in elixir umbrella application
body: <p>I have an elixir umbrella application (A) which has multiple applications underneath. One of them (B) is defined is separate repository and contains its own config (<code>config/config.exs</code>) file, mostly with default values. </p>
  
  <p>When adding application B to A and starting umbrella application, configuration for application B is not loaded. It looks like I need to explicitly include all configuration params for B in A config. </p>
  
  <p>I would expect that config for application B will be still available in application A and I would only have to override some specific values.</p>
  
  <p>Could anyone explain to me how I can achieve it without specifying all config params again in main application (A) config file?</p>