title: GraphQL - how to specify maximum String lengths in schema
body: <p>I want to tell GraphQL that my 'serialNumber' field is a String with a length of between 1 and 20 characters. I know to use the ! in the schema to make a field Required, but can I tell GraphQL that there is also a maximum field length?</p>
  
  <p>If I pass a null value in for a required String field, GraphQL will not accept it. I want it to behave the same way when it is passed a string that is longer than the maximum allowed length.</p>
  
  <p>I have looked at doing this two ways: 1) Add a 'maxlength' attribute to the field definition in the schema.graphql file. or 2) Create a new type and assign it a maximum length.</p>
  
  <p>I can't find any information on how to do it. Is is possible?</p>