The new ir_attachments are now stored as base64 strings. If i convert them manually to PDF, they work and can be opened. How can i override the download behaviour so that the files are decoded from base64 and converted to PDF when i download them? 

here is my xml, the field is attachment_ids:

string="Ansökningskomplettering">
    name="application_completion_main_group">
        name="rfq_id" />
        name="external_verification" invisible="1"/>
        name="rfq_applicant" invisible="1"/>
        name="rfq_coapplicant" invisible="1"/>
        name="type" />
        name="state" />
        name="applicant_id" domain="[('id', 'in', [rfq_applicant, rfq_coapplicant])]"/>
        name="attachment_ids" widget="many2many_binary"/>
        
class="oe_edit_only">
            name="manual_attachment_ids" widget="many2many_binary" string="Bifoga filer"/>
        

    
    
class="o_horizontal_separator ml-0 mt-4 mb-3 text-uppercase fw-bolder small">Meddelande till kund

    name="application_completion_comment" string="Meddelande till kund" header="Meddelande till kund">
        name="comment" nolabel="1"/>