WhatsApp messages now support tags and metadata

The WhatsApp messaging API brings tags and metadata in line with the rest of the platform. When you send a WhatsApp message, you can now attach:

• Tags: structured {name, value} labels, up to 20 per send, for low-cardinality dimensions like category or experiment_variant
• Metadata: an arbitrary JSON object (up to 2 KB) for your own per-send context, such as internal IDs

Both are echoed back on the message resource and on list results, which also gain a tag query parameter to filter by tag name or an exact name:value pair, matching the filtering already available for email and SMS messages.