Add rules for arrays and objects validation

[FluorescentHallucinogen]

Validate array argument. Something like:

type Mutation {
  updateUser(
    id: ID!
    name: String
    emails: [String!]! @constraint(
      minItems: 1,
      maxItems: 3,
      uniqueItems: true,
      format: "email" #applies to all items of array?
    )
  )
}

Validate object argument (useful when argument is an input type). Something like:

type Mutation {
  updateUser(
    data: UserUpdateInput! @constraint(
      name: { minLength: 5, maxLength: 40 },
      email: { format: "email" },
      age: { min: 18, max: 100 }
    )
    where: UserWhereUniqueInput!
  ): User!
}

input UserUpdateInput {
  name: String
  email: String
  age: Int
  verified: Boolean
}

[FluorescentHallucinogen]

See https://github.com/kristianmandrup/graphql-constraint-directive/blob/master/ComplexTypes.md for more info.