title: Auto generated Incrementing field for prisma
body: <p>I have created an entity called <code>Order</code> in my <code>datamodel.prisma</code> file. there it should have it's automatically generating field called <code>orderRef</code>. which should have an automatically generated incremental value for <code>createOrder</code> field of the Order entity for each mutation call.</p>
  
  <p>for the first Order the value of the 'orderRef' field should be OD1, the second Order should have the value OD2 for the field 'orderRef' and so on.
  eg: </p>
  
  <p>(OD1, OD2, ....... OD124, ..... )</p>
  
  <p>What is the easiest way to achieve this?
  yes <strong>the value should be String, instead of Number.</strong></p>