backoffice/image/get returns 'Not authorized file extension' for PDF file
should not be filtered for :
application/pdf,
application/rtf,
text/html,
text/plain,
text/richtext,
application/msword,
application/vnd.openxmlformats-officedocument.wordprocessingml.document,
application/vnd.ms-excel,
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet,
application/vnd.ms-powerpoint,
application/vnd.openxmlformats-officedocument.presentationml.presentation,
application/vnd.oasis.opendocument.text,
application/vnd.oasis.opendocument.spreadsheet,
application/vnd.oasis.opendocument.presentation