[cna] schema for CNA external resources

[geoberle]

this schema change introduces the external-resources extension for CNA

it covers the following modules

• null - for simple testing purposes without any prereqs on AWS accounts or clusters etc.
• aws-assume-role - for testing AWS assume-role access by CNA
• aws-rds - create an AWS RDS database

cna-experimental services as the provider, indicating the experimental nature of the integration and the CNAExperimentalProvisioner_v1 serves as the provisioner, wrapping an OCM organization and potentially adding additional config data (we will add a API URL override to this soon so we can target CNA API instances living outside of api.openshift.com)

Provisioner

$schema: /cna/experimental-provisioner-1.yml

name: app-sre
description: CNA provisioner for the app-sre OCM organization

ocm:
  $ref: /dependencies/ocm/stage.yml

<<<--- potential additional config options go here

Example RDS

The defaults files for CNA are now datafile schemas as well. As such they enable us to use references, e.g. a VPC

Here is the example of a defaults file for a production DB

$schema: /cna/aws-rds-config-1.yml
engine: postgres
username: postgres
engine_version: '14.2'
instance_class: db.m6.large
backup_retention_period: 7
db_subnet_group_name: default
allocated_storage: 200
max_allocated_storage: 1000
multi_az: true
vpc:
  $ref: /aws/some-account/vpcs/default-vpc.yml

and the external resource declaration that leverages it

$schema: /openshift/namespace-1.yml
...
externalResources:
- provider: cna-experimental
  provisioner:
    $ref: /cna/app-sre.yml
  resources:
  - provider: aws-rds
    identifier: my-db
    defaults:
      $ref: the-defaults-file.yml
    overrides:
      backup_retention_period: 14

design doc: https://gitlab.cee.redhat.com/service/app-interface/-/merge_requests/53097
ref: https://issues.redhat.com/browse/APPSRE-6295