Make the API Keys feature configurable, so that it can be either:

• Disabled
• Enabled only for admins
• Enabled for all users

This should be done through a new environment variable - the default should be 'Enabled only for admins'.

We should add a value to the Helm Chart to also be able to configure this setting at deployment time. Suggest we use console.enableApiKeys. This value can then be mapped through to the environment variable in the helm chart - use same pattern as tech preview: https://github.com/cloudfoundry/stratos/blob/master/deploy/kubernetes/console/templates/deployment.yaml#L278

This should be reflected in the front-end.

/info call returns metadata - backend can set metadata - tech preview - enableTechPreview

If we reconfigure to, say, admin only, then non-admin keys stop working. Equally, if we disable, all keys stop working.