Allow to use an alias in include syntax (or via new argument) to do a filtration by a relations

[alevshunov]

Raw model:

class User {
  id: int
  name: string
  roles: Role[]
}

class Role {
  id: int
  name: string
  users: User[]
}

What i'm looking for is to have ability to select user who has roleA and roleB assigned at the same time:
GET /rest/user?filter={exp: 'role.name = $a and role.name=$b', params: {a: 'roleA', b:'roleB'} - it will not work, so i'm looking for a way to define an alias for this magic, something like to (and yes, it could cause extra join):
GET /rest/user?include={path:'role', alias: 'r1'}&include={path:'role', alias:'r2'}&filter={exp:'r1.name = $a and r2.name=$b', params: {a:'roleA', b:'roleB'}
Or by using new argument:
GET /rest/user?alias={path:'role', name:'r1'}&alias={path:'role', name:'r2'}&filter={exp:'r1.name = $a and r2.name=$b', params: {a:'roleA', b:'roleB'}