title: RestKit 0.20.0 rc1 - Create request post with array of Strings
body: <p>is there a way to create arrays of Strings in requests?
  I did found some solutions for response, but the most of them are restkit 0.10.x or I did not understand them. (for example <a href="https://stackoverflow.com/questions/13054112/mapping-relationships-in-restkit-through-an-array-of-ids-doesnt-work">Mapping relationships in RestKit through an array of IDs doesn't work</a>)</p>
  
  <p>This is my setting:
  I use iOS 6 with core data and managed objects. My request should be like</p>
  
  <pre><code>{
   "attribute":["some text", "some more text", "and one more text"],
   "relationship":[some object data],
   "string":"some text"
  }
  </code></pre>
  
  <p>The entity is called "doRequest". "Relationship" is a relationship to an other managed object and "string" is an attribute. I would like to have "attribute" as an attribute, but there is no way to set "attribute" to an array of strings. So "attribute" is an one-to-many relationship to an entity "sub attribute" with attribute "text".</p>
  
  <p>My rest kit mapping:
      RKObjectMapping *subAttributeMapping = [RKObjectMapping requestMapping];
      [subAttributeMapping addAttributeMappingsFromArray:@[@"text"]];</p>
  
  <pre><code>RKObjectMapping *doRequestMapping = [RKObjectMapping requestMapping];
  [doRequestMapping addAttributeMappingsFromDictionary:@{
   @"string": @"string"}];
  
  [doRequestMapping addRelationshipMappingWithSourceKeyPath:@"attribute" mapping:subAttributeMapping];
  [doRequestMapping addRelationshipMappingWithSourceKeyPath:@"relationship" mapping:relationshipMapping];
  
  RKRequestDescriptor *requestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:doRequestMapping objectClass:[DoRequest class] rootKeyPath:nil];
  
  [objectManager addRequestDescriptor:requestDescriptor];
  </code></pre>
  
  <p>Restkit map this like:</p>
  
  <pre><code>{
   "attribute":[{"text":"some text"}, {"text":"some more text"}, {"text":"and one more text"}],
   "relationship":[some object data],
   "string":"some text"
  }
  </code></pre>
  
  <p>But that's not what I need.
  Could you please help me?</p>