title: do we need to define all Models in Fluent Api?
body: <p>In .Net Tutorial (in udemy and in some sites) I saw they declare the Fluent API for defining the relationship between Models.</p>
  
  <p>I tried to create models and not define relationship in Fluent API, it seems the migrations work and I checked on Mysql foreign key was well defined as well. </p>
  
  <p>I just need to know, when we really need to define the relationship between models with Fluent API (<code>OnModelCreating</code>)</p>
  
  <p>My Models:</p>
  
  <pre><code>using System.Collections.Generic;
  
  namespace CRSApp.API.Models
  {
      public class UserGroup
      {
          public int Id { get; set; }
          public string GroupName { get; set; }
  
          ICollection&lt;User&gt; Users { get; set; }
  
          ICollection&lt;UserGroupDetail&gt; Details {get; set;}
      }
  }
  
  
  namespace CRSApp.API.Models
  {
      public class UserGroupDetail
      {
          public int Id { get; set; }
          public int UserGroupId { get; set; }
          public int ModuleComponentId { get; set; }
  
          public UserGroup UserGroup { get; set; }
          public ModuleComponent ModuleComponent { get; set; }
      }
  }
  </code></pre>