oai pmh openaire description with wrong variables

[floriangantner]

Describe the bug
The service description of the openairecris oai pmh contains variables (from Dspace5) which are not substituted by default

To Reproduce
Steps to reproduce the behavior:

1. curl some endpoint, e.g. curl https://tore.tuhh.de/dspace-cris-server/oai/openairecris?verb=Identify

	<WebsiteURL>${dspace.url}</WebsiteURL>
	<OAIPMHBaseURL>http://${dspace.hostname}/oai/openairecris</OAIPMHBaseURL>

2. or curl some other endpoint https://publica-rest.fraunhofer.de/server/oai/openairecris?verb=Identify

	<WebsiteURL>https://publica.fraunhofer.de</WebsiteURL>
	<OAIPMHBaseURL>http://https://publica-rest.fraunhofer.de/server/oai</OAIPMHBaseURL>

3. the OAI Base URL (https://github.com/4Science/DSpace/blob/dspace-cris-7/dspace/config/crosswalks/oai/service-description.xml) is substituted from some property dspace.hostname or dspace.url from dspace5 and thus left blank. Modifications in the configuration more or less lead to invalid urls.
4. Note: changes on the configuration might have no effect if the oai.cache is oai.cache.enabled = true. The should be erased before!

Expected behavior
We expect to use the default dspace.server.url proeprty for this purpose.

Related work
Link to any related tickets or PRs here.