Make the custom check work in both embedded and external mode

Author: mauroservienti

src/ServiceControl.Audit.Persistence.RavenDB/MemoryInformationRetriever.cs

@@ -8,7 +8,10 @@ namespace ServiceControl.Audit.Persistence.RavenDB;
 
 class MemoryInformationRetriever(DatabaseConfiguration databaseConfiguration)
 {
-    readonly HttpClient client = new() { BaseAddress = new Uri(databaseConfiguration.ServerConfiguration.ServerUrl) };
+    // TODO what does a connection string look like? Is it only a URI or could it contain other stuff?
+    //   The ?? operator is needed because ServerUrl is populated when running embedded and connection string when running in external mode.
+    //   However the tricky part is that when tests are run they behave like if it was external mode
+    readonly HttpClient client = new() { BaseAddress = new Uri(databaseConfiguration.ServerConfiguration.ServerUrl ?? databaseConfiguration.ServerConfiguration.ConnectionString) };
 
     record ResponseDto
     {