title: How to do complex querying with logical operations by using searchkick
body: <p>Iam using <strong>searchkick</strong> library as an elasticsearch client for Product searching.
  <a href="https://github.com/ankane/searchkick" rel="noreferrer">https://github.com/ankane/searchkick</a></p>
  
  <p>It is possible to create 'OR' condition and 'AND' condition;</p>
  
  <p><strong>AND operation</strong>
  Product.search where: {price: {lte: 200}, in_stock: true} </p>
  
  <p><strong>OR operation</strong>
  Product.search where: {or: [[{in_stock: true}, {backordered: true}]]}</p>
  
  <p>But Iam stuck with creating <strong>multiple 'AND' 'OR'</strong> conditions with searchkick.</p>
  
  <p>I need something like</p>
  
  <p>A OR B OR ( C AND D )</p>
  
  <p>or I need like this, </p>
  
  <p>A AND B AND ( C OR D )</p>
  
  <p>Please guide me, how to achieve this</p>
  
  <p>Thanks</p>