Define a runtime component to hold nuxeo.conf properties for Drive

The Need

See TL-335 for details, but in short, we want to be able to define (Nuxeo Drive) application oriented properties and retrieve those values using a REST API.

The goal is to be able to use A/B testing or define which features/behaviors can the client-side application use or not.

New properties could be:

# Features
nuxeo.drive.feature.auto_update
nuxeo.drive.feature.direct_edit
nuxeo.drive.feature.direct_transfer
nuxeo.drive.feature.s3

# Behaviors
# nuxeo.drive.behavior.server_deletion

After retrieving such properties, they should be merged with one from the server configuration file (NXP-22946).

The current endpoind, SERVER_URL/drive/configuration will be reused to retrieve a JSON of those properties. This will ease the deloyment on the client side where no changes will be required.

Action Plan

Take inspiration from NXP-17673 to implement the ConfigurationService logic.

Expected Result

When done, accessing to the endpoint will:

• Retrieve "properties" from the old server's config and log a deprecation warning. We do not want to use that file anymore in a future release.
• Retrieve properties using the ConfigurationService.
• Merge properties together: properties from the CM will have the priority in case of duplicates.
• Return the final JSON.