Is it possible to acquire UUID from opaque global ID within custom database functions?
### Summary

I'm currently writing a custom database function that's meant to enable a new computed connection on one of my tables. The real functionality is more complex and a bit non-standard, but here's a simplified example of what I'm attempting to enable.

```graphql
{
  # connection automatically generated by postgraphile from record table
  recordConnection{
    edges {
      node {
        id
        # computed connection generated by a new function
        labeledValueConnection(matcherId: $selectedMatcherId) {
          labelRow
        }
        valueRow
      }
    }
  }
}
```

So far following [the docs](https://postgraphile.org/postgraphile/next/computed-columns) has just worked, which is awesome! I've seen that adding a parameter to the function exposes the parameter in the schema, which works great for me. The one thing I haven't figured out is how to get it so the schema can take in an opaque node ID on the request side, and the database function can acquire the related UUID of the actual record so I can join against it. 

I think I've seen [some mentions](https://discord.com/channels/489127045289476126/498852330754801666/1167134645696082002) that this is doable, but please let me know if I'm just completely off the mark. I've noticed a couple examples in the docs that do something similar in exposing new fields as ID parameters, but generally they seem to take in integers / the direct primary keys rather than the opaque global node id.

Thanks so much!

### Additional context

I'm using postgraphile beta 15 with the amber preset and relay preset, among some other customizations / plugins that shouldn't be relevant. 

Schema of my example would look something like this:

```sql
CREATE TABLE app_public.record (
    id uuid DEFAULT gen_random_uuid() NOT NULL,
    date timestamp with time zone,
    value_row smallint[]
);

CREATE TABLE app_public.matcher (
    id uuid DEFAULT gen_random_uuid() NOT NULL,
    name text
);

CREATE TABLE app_public.value_labels(
    id uuid DEFAULT gen_random_uuid() NOT NULL,
    matcher_id uuid,
    date timestamp with time zone,
    label text,
    value_location double precision
);
```

What my current solution sort of looks like;

```sql
CREATE TYPE app_public.labeled_value AS (
  label_row TEXT[]
);

CREATE FUNCTION app_public.record_labeled_value_connection(record app_public.record, matcher_id UUID)
RETURNS SETOF app_public.labeled_value AS $$
BEGIN
-- Magic happens! 
-- Grabs values out of value_labels based on the columns of the current record filtered to a certain matcher. 
-- Then builds and produces a row that is returned as a connection node.
END; 
$$ language plpgsql STABLE;
```