Add aliases at the schema level (In type)

Schema-level aliases can be useful if users decide to design their own sharding algorithm. Even better if we support a kind of “wildcards aliases”.

type User {
   name : <name.dgraph.*?number[0-300]> #This would create several (301) aliases 
   friend : <friend.dgraph.*?number[0-300]>
}

The wildcard would avoid add manually something like

type User {
   name : <name.dgraph.000>; <name.dgraph.001>; <name.dgraph.003>; <name.dgraph.004>
   (...)
}