Dynamically add new AETs

[feliwir]

We have a requirement that AEs can be added added dynamically at runtime.

My proposal would be to provide a POST /aets endpoint, which allows adding new AEs.
The payload would contain the host the AET and the port

[nickamzol]

A few thoughts on this:

• As we don't persist any state in DICOM-RST yet, dynamically registered AEs would be lost after a restart. Is this acceptable?
• The request body could be an ApplicationEntityConfig, but serialized as JSON instead of YAML.
• DELETE could be useful as well to remove AEs that are no longer needed.
• As this is an administrative operation, this should be disabled by default.
• Inspired by OAuth Dynamic Client Registration, I think we should have a list of "trusted hosts" to restrict malicious usage.

server:
  dynamic-registration:
    enabled: true
    allowed-hosts:
      - host: 192.168.0.1
        port: 4242