title: Firestore relationship
body: <p>Can someone explain how to organize the relationship between objects using Spring Boot and Firestore?</p>
  <p>I am using spring-cloud-gcp-starter-data-firestore and I have two objects that must be located in different collections:</p>
  <pre><code>@Document(collectionName = &quot;action_task&quot;)
  public class ActionTask {
  
      @DocumentId
      private String id;
      ...........................
      
      private EventRule eventRule;
  }
  
  @Document(collectionName = &quot;event_rule&quot;)
  public class EventRulePair {
  
      @DocumentId
      private String id;
  
      ...................
  
      private String code;
  
      private String eventType;
  
      private Instant createdAt;
  }
  </code></pre>
  <p>How organize relationships in the code and haw store in DB?</p>