Title: Odoo 18 - Send WhatsApp template via automated action after customer replies in discuss.channel

Description:

I'm trying to build a WhatsApp flow in Odoo 18:

1. Customer receives WhatsApp template with buttons ("Goed bevallen" / "Niet goed bevallen")
2. Customer clicks "Goed bevallen" → reply comes in as a discuss.channel message
3. Odoo should automatically send a second WhatsApp template as response

What works:

• Automated action triggers correctly on model "mail.message"
• Trigger: On save, filter: body contains "Goed bevallen"
• We can find the sale.order via the channel name
• We have the partner phone number

What doesn't work:

• Sending the WhatsApp template via code

Code tried so far:

python

# Attempt 1 - gives AttributeError
env["whatsapp.message"].create({...}).send()

# Attempt 2 - gives AttributeError  
env["whatsapp.message"].create({...}).button_send_whatsapp_template()

# Attempt 3 - no error but nothing sent
env["whatsapp.composer"].create({...}).action_send_whatsapp_template()

Question: What is the correct method in Odoo 18 to send an approved WhatsApp template via server action code?