title: Spring boot how to add a second datasource that may or may not exist
body: <p>I want to have an optional secondary database for my application such that if the secondary database exists on the deployed environment a repository can retrieve data from it, but if it does not exist, the application will still work fine with just the primary database, and the repository will behave in a way where the application can know this datasource isn't available. </p>
  
  <p>I can definitely think of ways of accomplish this type of thing, but I wonder if there is a more direct configuration type way of achieving this. Or if there is a pattern type way of handling that is preferable. </p>