Remove the manifest schema conversion machinery

[lubosmj]

This feature is no longer expected to be supported or maintained.

pulp_container/pulp_container/app/schema_convert.py

Line 23 in 4dfeb5c

class Schema2toSchema1ConverterWrapper:

pulp_container/docs/workflows/host.rst

Line 116 in 4dfeb5c

(schema 2), the manifests are rewritten into the old format (schema 1) on-the-fly by Pulp.

[lubosmj]

Additionally, we will remove the pyjwkest dependency from our requirements.

[lubosmj]

In the end, we would like to return 404 in case the client is requesting docker manifest v2 schema 1 instead of accepting what is available (manifest v2 schema 2).

pulp_container/pulp_container/app/registry.py

Line 216 in 59e06e5

return await Registry.dispatch_converted_schema(tag, accepted_media_types, path)

[lubosmj]

Based on docker documentation (https://docker-docs.uclv.cu/registry/spec/manifest-v2-2/#backward-compatibility), we will no longer support the following procedure:

If the manifest being requested uses the new format, and the appropriate media type is not present in an Accept header, the registry will assume that the client cannot handle the manifest as-is, and rewrite it on the fly into the old format.

Which is totally acceptable.