The http API has its first set of endpoints to implement the core aspects of
fetching and uploading layers. Uploads can be started and completed in a single
chunk and the content can be fetched via tarsum. Most proposed error conditions
should be represented but edge cases likely remain.
In this version, note that the layers are still called layers, even though the
routes are pointing to blobs. This will change with backend refactoring over
the next few weeks.
The unit tests are a bit of a shamble but these need to be carefully written
along with the core specification process. As the the client-server interaction
solidifies, we can port this into a verification suite for registry providers.
This changeset defines the application structure to be used for the http side
of the new registry. The main components are the App and Context structs. The
App context is instance global and manages global configuration and resources.
Context contains request-specific resources that may be created as a by-product
of an in-flight request.
To latently construct per-request handlers and leverage gorilla/mux, a dispatch
structure has been propped up next to the main handler flow. Without this, a
router and all handlers need to be constructed on every request. By
constructing handlers on each request, we ensure thread isolation and can
carefully control the security context of in-flight requests. There are unit
tests covering this functionality.
