fix checklist api links

api links in the checklist description box are broken when running on wwwint and wwwdev but working when running locally. They
The same problem is also in the $id attribute of the checklist's json schema, e.g. in https://wwwdev.ebi.ac.uk/biosamples/schema-store/registry/schemas/ERC000057%3A1.3 it has ` "$id": "https://json-schema-store/registry/schemas..."`

The URLS contain the name of the app's host inside its cluster, i.e. json-schema-store.
Since the desired value, i.e. `https://wwwdev.ebi.ac.uk/biosamples/schema-store` is not known to the app and is handled by the EBI traffic manager, the app needs to get this information somehow.

- [ ] fix $id url in json schema
- [ ] fix url in _links of rest api responses

Spring boot has a feature that knows to get the external host name [when running behind proxies](https://docs.spring.io/spring-boot/how-to/webserver.html#howto.webserver.use-behind-a-proxy-server) like EBI's traffic manager. This feature is controlled by setting the `server.forward-headers-strategy` configuration property.

I did not manage to get this to work.

Unlike common proxies that use `X-Forwarded-Host` and `X-Forwarded-Port` header, I noticed that our spring boot app has the value in the header Host. Both possible values of `server.forward-headers-strategy`: `native` and `framework` did not work when I tested on the k8s cluster.

This requires further investigation.