Changes to Mailchimp merge tags

Feature ID: CRMS-1680

When you enable Mailchimp integration, Sage CRM automatically adds a number of fields (also known as merge tags) to your Mailchimp audience. In Sage CRM 2024 R2, we did the following:

Renamed some of the merge tags to make their names consistent and avoid potential conflicts with field names in Sage CRM.
Unlinked some of the merge tags from the corresponding Sage CRM fields to reduce the number of merge tags used and let you add more custom Sage CRM fields.

In combination with the Add custom field to Mailchimp audience feature, this gives Mailchimp users more flexibility in selecting which Sage CRM fields to use in their Mailchimp campaigns. The number of custom fields a user can add to their Mailchimp audience depends on their Mailchimp price plan.