Auto generate 'owner' value for update operations if primary key contain owner field

[yaquawa]

Hi, I'm really appreciate your work on this, without this plugin, I would have had to quit using Amplify...!!

I found an issue with a usecase that the primary key contain owner field.

For instance:

type Review
  @model
  @key(fields: ["owner", "serviceId"])
  @auth(rules: [ { allow: owner } ]) 
{
  id: ID!
  serviceId: ID!
  owner: String! @auto
  service: Service @connection(fields: ["serviceId"])
  rating: Int
  title: String
}

Now, updateReview wouldn't allow user to specify the owner field, which is fine, but, because the owner is the partition key of the Review table, DynamoDB requires the the owner field to update the item. So to make this work, we have to generate the value of 'owner'.

sure I can use @auto(updatable: true), so I can manually input the owner field, but it really should be generated automatically in this case.

I saw you have already auto generated the createdAt field, why not for the owner as well?

so the logic would be

1. set ownerField default value to "owner".
2. check if @auth directive contains ownerField argument, if it is, set ownerField to that value.
3. check if fields argument of @key contains the value of ownerField.
4. if step 3 is true, set $context.args.input.${ownerField} to the incoming request's identity.