Set up a listener to capture notifications from the Supabase function and forward them to the external API.

This usually involves running a script or service that listens to the realtime channel:
```javascript
import { createClient } from '@supabase/supabase-js';

const supabaseUrl = 'https://xyzcompany.supabase.co';
const supabaseKey = 'your-anon-key';
const supabase = createClient(supabaseUrl, supabaseKey);

supabase
.from('your_table_name')
.on('INSERT', payload => {
fetch('https://external-api.com/endpoint', {
method: 'POST',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify(payload.new)
})
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.error('Error:', error));
})
.subscribe();
```

Replace the Supabase URL, API Key, table name, and external API endpoint with your actual values.