[Application Feature] Add gradual activation depending on user identifier

[gsoumier]

Add the possibility to add a graduation on application features in Tock studio to activate the feature only for a percentage of users. The graduation can be added in the feature state saved in Mongo database as an optionnal Int with a value between 0 and 100 Expected behaviour :

• FT DISABLED : DISABLED regardless of graduation saved
• FT ENABLED and no graduation (null value) : ENABLED
• FT ENABLED and graduation = 0 => DISABLED
• FT ENABLED and graduation = 100 => ENABLED
• FT ENABLED and graduation = x (between 1 and 99) => if(hash(userId) < x) ENABLED else DISABLED Where hash is a function which result is a number between 0 and 100 from the userId String