add a root level application identifier field

[concaf]

So right now, passing in multiple files does not work (#167), and we will be implementing merging of OpenCompose files https://github.com/redhat-developer/opencompose/issues/167#issuecomment-308050943 as a default behavior, but I think it would be cool to have a root level optional identifier like app or application or namespace, which allows defining the name of the larger application.

An example use case would be when we do a -

opencompose convert -f wordpress.yaml -f nginx.yaml

• nginx.yaml -

  
  version: 0.1-dev
  app: nginx                      # note: the root level application identifier is nginx
  services:

• name: web # note: the name of the service is web containers:

  • image: nginx name: nginx ports:
  • port: 80

• wordpress.yaml -

  
  version: '0.1-dev'
  app: wordpress                  # note: the root level application identifier is wordpress
  services:

• name: database containers:

  • image: mariadb:10 name: mariadb ports:
  • port: 3306

• name: web # note: the name of the service is web containers:

  • image: wordpress:4 name: wordpress ports:
  • port: 80 type: external

So, when we pass these 2 files to opencompose convert, then the service web from app: nginx and app: wordpress does NOT get merged because of different root level app identifier.

This is more for namespacing the applications in the spec itself.

Thoughts?

CC: @kadel