Create a JSON-schema for the Devfile

[sleshchenko]

Description

Create a JSON-schema for the Devfile.
It's a well-known standard for defining data formats. It will help with the discussion and allows to generate doc and API source code too.

[l0rd]

@sleshchenko I have moved devfile to https://github.com/redhat-developer/devfile

[mshaposhnik]

Json validation library research:

1. Officially recommended, supports latest v7 draft, but requires external repo set-up: https://github.com/everit-org/json-schema
2. Popular one, a continuation of popular fge library https://github.com/java-json-tools/json-schema-validator Supports only v.4 draft ATM
3. Also good one, but only draft v.4 support now (planned to update soon) https://github.com/networknt/json-schema-validator

Libraries 2 and 3 already have theirs CQ-s approved (or maybe just piggyback ir required)

Unfortunately, none of them supports validating yaml directly. So for phase 1 we can convert incoming yaml to JSON before validation.

So, for me lib no.2 looks most reasonable for this moment,

[mshaposhnik]

The best way to generate POJO from schema is seems to be https://github.com/joelittlejohn/jsonschema2pojo library. We shall review it and start a CQ process if we found it acceptable for us.

[mshaposhnik]

Will be closed together with merge of #11998