OCI-based registry support

[gorkem]

Is your feature request related to a problem? Please describe.
Provide a devfile registry solution that is easier to manage, takes advantage of the existing mechanisms of access control, distribution, caching, proxy

Describe the solution you'd like
Existing proposal

Additional context

[elsony]

MVP:

• Initial setup of a devfile registry
  • Bootstrap a basic OCI registry with devfiles from a devfile registry on GitHub (Bootstrap a basic OCI registry with devfiles from a devfile registry on github #143)
• Define the structure of the devfile registry (Define the structure of the devfile registry #226)
• Initial design on life cycle of devfile registry (start, stop, restart) (Initial design on life cycle of devfile registry (start, stop, restart) #162)
• Formalize and define schema for devfile registry metadata (index.json) (Formalize and define schema for devfile registry index (index.json) #135)
• Initial design on the packaging of devfile registry for deployment (Initial design on packaging of devfile registry for deployment #163)
• Re-write the OCI registry metadata container in Go (Re-write the OCI registry metadata container in Go #188)
• Deployment of devfile registry in cluster (Deployment of devfile registry in cluster #190)
• Define onboarding requirement for a stack to be added to a public registry (include documentation on the devfile public website) (Define onboarding requirement for a stack to be added to a public registry (include documentation on the devfile public website) #191)
• Build tools for generating registry based on registry/catalog info on a GitHub repo
  • Build tool for converting the devfile registry git repo content to build the image for the devfileIndexImage (Build tools for generating registry based on registry/catalog info on a github repo #164)
  • Include schema validation and other stack validation as part of the index.json generator (Include schema validation and other stack validation as part of the index.json generator  #222)
• Define a public common devfile registry that can be shared across different tools (Define a public common devfile registry that can be shared across different tools #225)
• Basic registry access function library (Basic registry access function library #224)
• Update odo to use the new registry access library (# TBD on odo repo)

MVP+:

• Handle update on the content of the devfile registry, e.g. add and remove a stack, update of the content of stack, update of metadata (index.json) of the stack.
• Validation support on build tool to standardize onboarding requirement for a stack to be added to a public registry.
• Allow stack contents to be stored under stack owned repos
• Define a mechanism for stack providers to provide multiple versions of a given stack
• Secured registry support
• Offline registry support (Devfile registry air gap/offline installation #329)
• Registry on cluster discovery
• Add hooks to the index.json generator more extensible to allow custom validation and auto-tag generation (Language & Framework detection for Devfile Applications #223)
• Install devfile registry in a cluster using Helm (Install devfile registry in a cluster using Helm #237)