Fix: Delete Failures in Postgres Handled

[GnosisAI]

This pull request fixes an issue in our Postgres consumer's handling of delete events, which was reported in issue #22.

In delete events, Postgres does not provide columnnames or columnvalues but instead only sends the id of the deleted row along with all column values. Our consumer now correctly captures the id from oldkeys to construct the necessary data for delete events.

Changes:

• Updated delete event handling to fetch the id from change["oldkeys"]["keynames"][0] and change["oldkeys"]["keyvalues"][0].

Here's an example of a delete event change object that this fix accommodates:

{
  "kind": "delete",
  "schema": "public",
  "table": "products",
  "oldkeys": {
    "keynames": ["id"],
    "keytypes": ["integer"],
    "keyvalues": [25]
  }
}

[long2ice]

Thanks!