Add plans/subscriptions management

[gahabeen]

Summary

Integrate logic in order to:

• give permissions based on a subscription a user has
• keep track of usage to apply limitations (ex: max number of documents owned in a collection)

What it implies:

• Plans are roles named biota.plan.<id>
• Relation between a user (or any document) and plan is called a subscription
• Relation is determined by a _membership.plan field on a document

Basic example

Plan definition:

// API is very similar to db.role() if not the same
db.plan('basic').insert()

// update permissions
db.plan("basic").privileges.set({
  resource: Collection('todos'),
  rights: {
    insert: ['owner']
  }
})

// expire in an hour
db.plan('basic').expireIn(3600)

// list plans
db.plans.findAll()

Motivation

Properly manage the user's permissions through a common model of plans/subscriptions.