Devfile registry air gap/offline installation

[elsony]

A devfile refers to various resources, e.g. container images, projects, and starter projects. The current devfile registry currently does not store those supporting resources as part of the registry. This means that the user will need to have access to those resources when using those devfiles. This item adds support to install a devfile registry in an air-gapped environment.

Design doc: https://docs.google.com/document/d/15PpUGiWOXjfQ5GtJFPHp0cG73jtpmw1H9AkCrnJVD2E/edit?usp=sharing

Acceptance criteria:

1. Implement according to the design on the design doc so that the offline installation is self-contained and can be installed without internet access
2. Testing to verify the implementation according to the design doc
3. Document on how to do air gap installation

Related Issues
Child issues for this EPIC:

• Package starter projects in offline registry #1203
• Package uri links in offline registry #1220
• add dockerfile to support offline registry builds registry#197
• Add documentation for automated air gap registry installation #1222

[rkratky]

Docs JIRA issue: https://issues.redhat.com/browse/RHDEVDOCS-2872

[nickboldt]

Support for offline/airgap is a vital requirement for getting any of this new registry stuff into CRW, as CRW registry builds are by default offline so they can be used behind an airgap/proxy.

Please don't forget about this requirement when designing how to build your registries.

[kim-tsao]

We should also review how the devfile library can access offline parent resources from the registry, especially since a git clone is being done

[michael-valdron]

Adding this to triage as there seems to be criteria still being worked out.

cc: @elsony