fix(db-postgres): joins to self collection

[r1tsuu]

What?

With Postgres, before join to self like:

import type { CollectionConfig } from 'payload'

export const SelfJoins: CollectionConfig = {
  slug: 'self-joins',
  fields: [
    {
      name: 'rel',
      type: 'relationship',
      relationTo: 'self-joins',
    },
    {
      name: 'joins',
      type: 'join',
      on: 'rel',
      collection: 'self-joins',
    },
  ],
}

wasn't possible, even though it's a valid usage.

How?

Now, to differentiate parent self_joins and children self_joins we do additional alias for the nested select - "4d3cf2b6_1adf_46a8_b6d2_3e1c3809d737":

select 
  "id", 
  "rel_id", 
  "updated_at", 
  "created_at", 
  (
    select 
      coalesce(
        json_agg(
          json_build_object('id', "joins_alias".id)
        ), 
        '[]' :: json
      ) 
    from 
      (
        select 
          "created_at", 
          "rel_id", 
          "id" 
        from 
          "self_joins" "4d3cf2b6_1adf_46a8_b6d2_3e1c3809d737" 
        where 
          "4d3cf2b6_1adf_46a8_b6d2_3e1c3809d737"."rel_id" = "self_joins"."id" 
        order by 
          "4d3cf2b6_1adf_46a8_b6d2_3e1c3809d737"."created_at" desc 
        limit 
          $1
      ) "joins_alias"
  ) as "joins_alias" 
from 
  "self_joins" 
where 
  "self_joins"."id" = $2 
order by 
  "self_joins"."created_at" desc 
limit 
  $3

Fixes #10144

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🚀 This is included in version v3.12.0