deposit: removes useless alert attribute appended to the class

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
deposit: fixes field messages

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

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
deposit: adds ArXiv syntax regex validator

* This Regex supports both the new and the old ArXiv id formats

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
utils: adds DOI json data fetching

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
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 <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
deposit: adds json api to fetch doi from crossref

* This searches the DOI on crossref and returns the result
  as JSON format, also handles if the DOI isn't found or
  it's malformed

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>