Upgrade all packages and get full support of null safety

[ghost]

Hi @lucafluri ,

Hope you are all well ! And happy new year too :-)

I was testing your project, that I am considering actually as one of the greatest of the flutter ecosystem (in terms of complexity and business value), but I was wondering if you should not migrate to full support of null safety and all your packages btw (firebase, firestore, etc...).

What do you think about that ?

Cheers, Luc