docs: remove vault blueprint

Moved here:
https://wiki.softwareheritage.org/index.php?title=Vault_Blueprint

docs/vault-blueprint.md

-Software Heritage Vault
-=======================
-
-Software source code **objects**---e.g., individual source code files,
-tarballs, commits, tagged releases, etc.---are stored in the Software Heritage
-(SWH) Archive in fully deduplicated form. That allows direct access to
-individual artifacts but require some preparation, usually in the form of
-collecting and assembling multiple artifacts in a single **bundle**, when fast
-access to a set of related artifacts (e.g., the snapshot of a VCS repository,
-the archive corresponding to a Git commit, or a specific software release as a
-zip archive) is required.
-
-The **Software Heritage Vault** is a cache of pre-built source code bundles
-which are assembled opportunistically retrieving objects from the Software
-Heritage Archive, can be accessed efficiently, and might be garbage collected
-after a long period of non-use.
-
-
-Requirements
-------------
-
-* **Shared cache**
-
-  The vault is a cache shared among the various origins that the SWH archive
-  tracks. If the same bundle, originally coming from different origins, is
-  requested, a single entry for it in the cache shall exist.
-
-* **Efficient retrieval**
-
-  Where supported by the desired access protocol (e.g., HTTP) it should be
-  possible for the vault to serve bundles efficiently (e.g., as static files
-  served via HTTP, possibly further proxied/cached at that level). In
-  particular, this rules out building bundles on the fly from the archive DB.
-
-
-API
----
-
-All URLs below are meant to be mounted at API root, which is currently at
-<https://archive.softwareheritage.org/api/1/>. Unless otherwise stated, all API
-endpoints respond on HTTP GET method.
-
-
-## Object identification
-
-The vault stores bundles corresponding to different kinds of objects. The
-following object kinds are supported:
-
-* directories
-* revisions
-* repository snapshots
-
-The URL fragment `:objectkind/:objectid` is used throughout the vault API to
-fully identify vault objects. The syntax and meaning of :objectid for the
-different object kinds is detailed below.
-
-
-### Directories
-
-* object kind: directory
-* URL fragment: directory/:sha1git
-
-where :sha1git is the directory ID in the SWH data model.
-
-### Revisions
-
-* object kind: revision
-* URL fragment: revision/:sha1git
-
-where :sha1git is the revision ID in the SWH data model.
-
-### Repository snapshots
-
-* object kind: snapshot
-* URL fragment: snapshot/:sha1git
-
-where :sha1git is the snapshot ID in the SWH data model. (**TODO** repository
-snapshots don't exist yet as first-class citizens in the SWH data model; see
-References below.)
-
-
-## Cooking
-
-Bundles in the vault might be ready for retrieval or not. When they are not,
-they will need to be **cooked** before they can be retrieved. A cooked bundle
-will remain around until it expires; at that point it will need to be cooked
-again before it can be retrieved. Cooking is idempotent, and a no-op in between
-a previous cooking operation and expiration.
-
-To cook a bundle:
-
-* POST /vault/:objectkind/:objectid
-
-  Request body: **TODO** something here in a JSON payload that would allow
-  notifying the user when the bundle is ready.
-
-  Response: 201 Created
-
-
-## Retrieval
-
-* GET /vault/:objectkind
-
-  (paginated) list of all bundles of a given kind available in the vault; see
-  Pagination. Note that, due to cache expiration, objects might disappear
-  between listing and subsequent actions on them.
-
-  Examples:
-
-  * GET /vault/directory
-  * GET /vault/revision
-
-* GET /vault/:objectkind/:objectid
-
-  Retrieve a specific bundle from the vault.
-
-  Response:
-
-  * 200 OK:        bundle available; response body is the bundle
-  * 404 Not Found: missing bundle; client should request its preparation (see Cooking)
-
-
-References
-----------
-
-* [Repository snapshot objects](https://wiki.softwareheritage.org/index.php?title=User:StefanoZacchiroli/Repository_snapshot_objects)
-* Amazon Web Services,
-  [API Reference for Amazon Glacier](http://docs.aws.amazon.com/amazonglacier/latest/dev/amazon-glacier-api.html);
-  specifically
-  [Job Operations](http://docs.aws.amazon.com/amazonglacier/latest/dev/job-operations.html)
-
-
-TODO
-====
-
-* **TODO** pagination using HATEOAS
-* **TODO** authorization: the cooking API should be somehow controlled to avoid
-  obvious abuses (e.g., let's cache everything)
-* **TODO** finalize repository snapshot proposal