Returns all P11Ds in a single PDF file for the TaxYear and Employer specified
If you set the accept header to TextHtml then unlike other reports the html is NOT in the ```Content``` field.
As there are multiple HTML documents they are encoded as a JSON array of strings in the ```Model``` field.
Deprecation notice: Accept: application/pdf returns a PDF link and is deprecated. Use Accept: application/octet-stream to retrieve PDF bytes through the authenticated API. The end-of-life date for PDF-link responses is 1st February 2027. Legacy PDF-link responses include Deprecation (RFC 9745 date @<unix-seconds>), Sunset, Warning, and optional Link headers.