title: Jhipster - setting up many to many relationship for user-entities
body: <p>Want to create entity called Friendship and want to leverage the User entity that's part of Jhipster,
  But I keep getting this invalid-relationship error (full error below). </p>
  
  <p>User has friends (user entities) and vice-versa</p>
  
  <pre><code>
  entity UserExtended {
  
  }
  entity Friend{
      status Boolean, 
      modified LocalDate,
      created LocalDate
  }
  relationship OneToOne {
      UserExtended{user(login)} to User
  }
  
  relationship OneToMany {
      UserExtended{friends} to Friend{user}
  }
  
  relationship ManyToOne {
      UserExtended{friend} to UserExtended{users}
  }
  
  entity Post {
      owner UserExtended,
      content String,
      dateCreated LocalDate 
  }
  
  entity Like {
      likedBy UserExtended,
      post Post,
      dateCreated LocalDate   
  }
  
  entity Comment {
      postedBy UserExtended,
      post Post,
      dateCreated LocalDate
  }
  
  
  relationship OneToMany {
    UserExtended{post} to Post{user}
  }
  
  relationship OneToMany {
    Like{post} to Post{like}
  }
  
  relationship OneToMany {
    Comment{post} to Post{comment}
  }
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>Error: Can't add invalid relationship. Error: In the Many-to-One relationship from UserExtended to UserExtended, only unidirectionality is supported, you should either create a bidirectional One-to-Many relationship or remove the injected field in the destination entity instead.
  Error while parsing applications and entities from the JDL Error: Can't add invalid relationship. Error: In the Many-to-One relationship from UserExtended to UserExtended, only unidirectionality is supported, you should either create a bidirectional One-to-Many relationship or remove the injected field in the destination entity instead.
  Error: Can't add invalid relationship. Error: In the Many-to-One relationship from UserExtended to UserExtended, only unidirectionality is supported, you should either create a bidirectional One-to-Many relationship or remove the injected field in the destination entity instead.
  </code></pre>