Support orderBy aggregates based on child tables

[bossjapzz]

Describe the bug Support orderBy aggregates based on child tables

To Reproduce Steps to reproduce the behavior:

1. just add order by to your query but you don't have an option to order by related tables (child table)

Expected behavior Based from hasura

[bossjapzz]

The most common operations are: count, max, min

[bossjapzz]

other operations aside from: standard deviation and variance is: avg, sum

[bossjapzz]

Another example is ordering POSTS by REACTIONS count

query MyQuery {
  GroupContent_connection(order_by: {GroupContentReactions_aggregate: {count: desc}}) {
    edges {
      node {
        id
        GroupContentReactions_aggregate {
          aggregate {
            count
          }
        }
      }
    }
  }
}

[cpursley]

Hasura compatibility would be really wonderful.