Add validation and usage logics into the model
Add validation and usage logics into the model

ISIFoundation/influenzanet-website,fajran/django-loginurl,vanschelven/cmsplugin-journal,uploadcare/django-loginurl,ISIFoundation/influenzanet-website,ISIFoundation/influenzanet-website,ISIFoundation/influenzanet-website,ISIFoundation/influenzanet-website,ISIFoundation/influenzanet-website,ISIFoundation/influenzanet-website