For sending a whatsapp template under certain conditions (maybe something happening in your database a new sale order) you can use automated actions and execute code, in code the sending of a whatsapp message looks something like this:
composer = env['whatsapp.composer'].create({

                    'res_model': 'whatsapp.message',

                    'res_ids': str([record.id]),

                    'wa_template_id': wa_template_id,

                    'batch_mode': False,

                    'phone': record.mobile_number,

                    'free_text_1': record.body or '',

                })

                composer.action_send_whatsapp_template()