Variable Modes: - custom - Use the provided value directly -
contactfield - Look up the value from the contact database using the field
name
Templates must be pre-approved by WhatsApp before use. Variable names must
match template placeholders exactly. Contact field lookups are case-sensitive.
Use the clientId parameter to track messages in your own system. This ID
will be returned in webhooks and status updates.
Media URLs (headerMediaUrl) must be HTTPS and publicly accessible. Templates
with media headers require a valid URL to be provided.