Support mandatory and opt-out deployment activation

[gberche-orange]

Is your feature request related to a problem? Please describe.

As a service author, in order to reduce the amount of release note documentation necessary to explicitly enable mandatory components, I need to specify that a component is mandatory and does not require opt-in through enable-deployment.yml config artefact.

Describe the solution you'd like

A flag in deployment-dependencies.yml such as deployment.bosh-deployment.resources.secrets.enable-deployment=always|opt-in|opt-out

when set to :

• always: the deployment is systematically enabled regardless of the presence/absence of enable-deployment.yml or disable-deployment.yml
• opt-in: (also default when unspecified) the deployment is only enabled in presence of enable-deployment.yml.
• opt-out: the deployment is only enabled in presence of disable-deployment.yml

This triggers an error during pipeline generation to have both enable-deployment.yml and disable-deployment.yml for a given deployment in the config repo

Describe alternatives you've considered

• Renaming deployment-dependencies.yml to a more generic name such as deployment-settings.yml and use a more meaningfull property naming such as deployment.bosh-deployment.enable-deployment=always|opt-in|opt-out

Additional context

Relates to https://github.com/orange-cloudfoundry/paas-templates/issues/342

This might also address #201 and #67