demosite: update demosite package for create/populate

* Changes from invenio_demosite to invenio_demosite.base

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
installation: MANIFEST template fix

* Fixes the MANIFEST template to include all jsonext configuration
  files.

Co-authored-by: Esteban J. G. Gabancho <egabancho@gmail.com>
Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
deposit: removes useless alert attribute appended to the class

Signed-off-by: Pedro Gaudêncio <pmgaudencio@gmail.com>
deposit: fixes field messages

* Fixes field info/warning/error/success/danger messages

Signed-off-by: Pedro Gaudêncio <pmgaudencio@gmail.com>
deposit: adds ArXiv syntax regex validator

* This Regex only supports the new ArXiv id format

Signed-off-by: Pedro Gaudêncio <pmgaudencio@gmail.com>
utils: adds DOI json data fetching

Signed-off-by: Pedro Gaudêncio <pmgaudencio@gmail.com>
deposit: adds hold_for_upload default variable

* Adds default value so the deposit submission is
  skiped if no value is set in child classes

Signed-off-by: Pedro Gaudêncio <pmgaudencio@gmail.com>
deposit: adds holding pen task for ongoing depositions

* This task adds the deposition to the Holding Pen so
  it gets approved or rejected by an administrator

Signed-off-by: Pedro Gaudêncio <pmgaudencio@gmail.com>