Circular references cause infinite loop

[lpoulier-vhs]

If there are circular references in the input types of the consumed graphql schema, the plugin will enter an infinite loop as it recursively processes each input type.

Eg: This schema generated by prisma-typegraphql:

input NestedStringFilter {
  contains: String
  endsWith: String
  equals: String
  gt: String
  gte: String
  in: [String!]
  lt: String
  lte: String
  not: NestedStringFilter
  notIn: [String!]
  startsWith: String

This could be handled by keeping track of the Set of processed types and skipping those already processed.