Graphql-engine: incorrect error code when insertion check constraint fails

[0x777]

{
  "errors": [
    {
      "path": "$",
      "error": "Check constraint violation. insert check constraint failed",
      "code": "postgres-error"
    }
  ]
}

It shouldn't be postgres-error, should either be permission-error or access-denied.

[shahidhk]

[via thangngoc89#8365 on discord]

[shahidhk]

@thangngoc89 candidate for alpha13