Move django-based uncloud to top-level

doc/README-object-relations.md

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+## Introduction
+
+This article describes how models relate to each other and what the
+design ideas are. It is meant to prevent us from double implementing
+something or changing something that is already solved.
+
+
+## Products
+
+A product is something someone can order. We might have "low level"
+products that need to be composed (= higher degree of flexibility, but
+more amount of details necessary) and "composed products" that present
+some defaults or select other products automatically (f.i. a "dual
+stack VM" can be a VM + a disk + an IPv4 address).
+
+
+## Bills
+
+Bills represent active orders of a month. Bills can be shown during a
+month but only become definitive at the end of the month.
+
+## Orders
+
+When customer X order a (set) of product, it generates an order for billing
+purposes. The ordered products point to that order and register an Order Record
+at creation.
+
+Orders and Order Records are assumed immutable => they are used to generate
+bills and should not be mutated. If a product is updated (e.g. adding RAM to
+VM), a new order should be generated.
+
+The order MUST NOT be deleted when a product is deleted, as it is used for
+billing (including past bills).
+
+### Order record
+
+Used to store billing details of a product at creation: will stay there even if
+the product change (e.g. new pricing, updated) and act as some kind of archive.
+Used to generate bills.
+
+## Payment Methods
+
+Users/customers can register payment methods.
+
+## Sample flows / products
+
+### A VM snapshot
+
+A VM snapshot creates a snapshot of all disks attached to a VM to be
+able to rollback the VM to a previous state.
+
+Creating a VM snapshot (-product) creates a related order. Deleting a
+VMSnapshotproduct sets the order to deleted.
+
+### Object Storage
+
+(tbd by Balazs)
+
+### A "raw" VM
+
+(tbd by Ahmed)
+
+### An IPv6 only VM
+
+(tbd by Ahmed)
+
+### A dual stack VM
+
+(tbd by Ahmed)
+
+### A managed service (e.g. Matrix-as-a-Service)
+
+Customer orders service with:
+	* Service-specific configuration: e.g. domain name for matrix
+	* VM configuration:
+		- CPU
+		- Memory
+		- Disk (soon)
+
+It creates a new Order with two products/records:
+	* Service itself (= management)
+	* Underlying VM