CLI is able to create a event receiver group without a type

Need to make sure we are requiring all appropriate fields for create mutations in graphql 

Require the following fields for event group receivers:  

  name: String!
  type: String!
  version: String!
  description: String!
  enabled: Boolean!
  event_receiver_ids:  [ID!]!

https://github.com/sassoftware/event-provenance-registry/blob/main/cli/cmd/group/create.go 