title: Crnk JsonApiRelation, OneToMany and filtering implementation
body: <p>I use crnk (JSON-API) in java project and I have 3 questions regarding its usage with spring boot and jpa - haven't found exact implementation details in documentation.</p>
  
  <ol>
  <li><p>For example, I have 2 entities and respective tables:</p>
  
  <pre><code>@Entity
  @JsonApiResource(type = "employee")
  public class Employee {
      @Id
      @JsonApiId
      private int id;
  
      private String name;
  
      @ManyToOne
      @JoinColumn(name = "typeId")
      private EmployeeType employeeType; //stored in table as typeId
  }
  
  @Entity 
  @JsonApiResource(type = "type")
  public class EmployeeType {
      @Id
      @JsonApiId
      private int id;
  
      private String typeName;
  
      private int salary;
  }
  </code></pre></li>
  </ol>
  
  <p>How should JsonApiRelation be introduced in order to be able to call "/employee/1" and "/employee/1/type" urls?</p>
  
  <ol start="2">
  <li><p>For example there is one more entity. </p>
  
  <pre><code>@Entity
  @JsonApiResource(type = "project")
  public class Project {
      @Id
      @JsonApiId
      private int id;
  
      private String supervisorName;
  
      private String projectName;
  }
  </code></pre></li>
  </ol>
  
  <p>First, I'd like to have List of Projects for each Employee, where he is a supervisor, joint by name and have it listed as attribute in Json. </p>
  
  <p>Tried implementing it with @OneToMany and @JoinColumn annotations but got StackOverflowException. How could this be implemented. And second, how could this be implemented with Relation? Like "/employee/1/projects" url.</p>
  
  <ol start="3">
  <li>How should I implement custom filtering of results for findAll method? For example, I have a List of all Employees, but I'd like to exclude some of them from the response. Which class/method should be introduced for this behaviour?</li>
  </ol>