upsertContact creates a contact or updates the record with the same email. It
can set attributes, add list memberships, and change marketing blocklists.
Example
Inputs
email is required. attributes values may be string, number, boolean, or
string array; Automate.ax uppercases attribute names before sending them.
Optional extId, list names or positive IDs, emailBlacklisted,
smsBlacklisted, smtpBlacklistSender, and forceMerge are supported.
forceMerge defaults to false; account selects the Brevo binding.
Output
Returns{ id: number } for the created or updated contact. Attribute
definitions must already exist in the Brevo account and values must match their
configured types. List names are resolved case-insensitively by exact name;
missing or ambiguous names fail before the contact write.