Get Proposal Details (Anon)

Returns proposal information for the anonymous acceptance page.

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