Add application registry functionality to the service registry

[tdudgeon]

As has been discussed, we wish to add the ability for applications to register themselves when they start so that we have a dynamic list of end user applications that are running in a VRE. This will replace the current static landing page.

To achieve this we believe that routes for any application that can be accessed by an end user will be annotated with key information that can be used by the registry to generate the page. This will probably include:

• application name
• application description
• category
• link to page for that application on the ORN website

Whilst quite similar to the existing service registry this information is quite different and will appear in a different page.

Ideally the location of this page can be https://home.prod.openrisknet.org/ so that we can keep the same link.