Replace date_end by date_end_memb in voucher_pdf. Close #315

See the issue for details.

Closes #317 .

The Entire LDAP infrastructures now relies on signals rather than direct function calls and is in its own app. This means it can be deactivated, but also that we can easily plug new services in addition to LDAP, such as OAuth.

Closes issue #270

We made it this far folks.

Closes #307


Co-authored-by: Jean-Romain Garnier <jean-romain.garnier@supelec.fr>
Co-authored-by: Hugo Levy-Falk <hugo@klafyvel.me>