Get Engagement Details

Returns engagement information for the anonymous acceptance page.

Requires a valid engagement GUID that has not yet been accepted or rejected.
Returns tenant details, content blocks, and engagement summary.

Optional Query Parameters:

• ddCallbackUrl: The callback URL to redirect to after Direct Debit mandate setup is complete.
  Required if you want to receive a Direct Debit mandate URL in the response.
  The mandate URL will only be generated if the tenant has RequestDDMandate enabled and a Direct Debit connection configured.
• preview: When true, skips updating LastViewed timestamp and Sent→Viewed status transition.
  Used by practice staff to preview the acceptance page without affecting engagement tracking.