GDPR compliance: Allow the export of user data

[Ash-Crow]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe. As per the GDPR, the user has a right to access data we have about them (Article 15) and to export it in a portable way (Article 20)

Right now, we already allow users to export a document in a portable way in various formats, but there is no way to make a full export of all their docs, nor see what metadata we have about them (except asking through the help chatbot or via email at lasuite -AT- numerique.gouv.fr, which should then be manually processed.)

Describe the solution you'd like

• There should be links to the legal mentions and privacy notice pages somewhere in the interface, the latter of which should include a button to ask the export of user data.
• When a user presses the button, they get a notification saying that the data is being prepared and will be sent to them shortly.
• They receive an email with a link to a secure platform (https://francetransfert.numerique.gouv.fr/ ?) with an archive of everything:
  • Docs exported in markdown (+ other formats?)
  • Metadata we have about the account (eg. secondary linked accounts when #1616 is merged)
  • data we have about them in other tools linked to Docs (eg. Crisp requests)
  • what data we transmit to third parties, if any.

Other notes/questions

• Should this be made only at the Docs level or should the export have all the Suite Numérique tools included?
• The PR checklist should include a checkbox indicating if it includes new content that should be part of the user data export.