Pre-imports failing due to unsupported CNAB media types
Context
Found during gitlab#350920 (closed).
Problem
A few pre-imports failed due to:
1 error occurred:
* pre importing tagged manifests: pre importing manifest: pre importing manifest list: unknown media type: application/vnd.cnab.config.v1+json
Solution
Add support for application/vnd.cnab.config.v1+json
and while at it also application/vnd.cnab.bundle.config.v1+json
.