Odoo Release Updates

[REF] mail: activities use user_id rather than persona

[IMP] point_of_sale, pos_*: improve self order table management

[FIX] mrp_subcontracting: small cosmetic changes

[IMP] core: bump master release to 19.1 alpha

[IMP] web: list multi edit: display M2M changes in modal

[IMP] account: Move some helpers in another section + merge_tax_details in js

[IMP] mail: use composerHtml for restore

[FIX] hw_drivers: prevent duplicated actions

[IMP] website: update some navbar design / fix issues

[FIX] web: burger user menu click doesn't close it

[IMP] spreadsheet: update o_spreadsheet to latest version

[IMP] website_slides: require file upload/link for document and image content

[IMP] mass_mailing: reorganize style files

[FIX] mrp_subcontracting: clean code

[FIX] website: fix header alignment and position options

[IMP] mass_mailing: design option for margin bottom on paragraphs and headings

[IMP] website: update some header options availability

[FIX] html_editor: fix references and lint errors

[FIX] website: restore background colors for translator indicators

[IMP] account_peppol: add peppol_metadata

[FIX] sms_twilio: fix failure types support on notifications / traces

[FIX] account: warning on currency decimal change independent of entries

[FIX] spreadsheet: display value for id fields in pivots