TextTemplateResourceReference registration

[Jesse Long]

Hi Wicket Devs,

TextTemplateResourceReference is dynamic, it contains a Map<String, 
Object> to populate a normal text resource.

issue 1: It cannot be shared between servers in a cluster, I think we 
should add some javadocs explaining this. The old, "if your cluster does 
not support sticky sessions, this will not work" bit.

issue 2: The problem is that it is registered using the same key in the 
ResourceReferenceRegistry each time. In 1.5.5 only the first instance 
was registered, but I see this is fixed, at least in master. Now, it 
deregisters the previous instance and registers a new instance. This is 
not very thread safe. Think multiple instances created in different 
sessions.

I was wondering, would it be possible to register 
TextTemplateResourceReference using a autogenerated "resource name" 
(param 2 to ResourceReference constructor), and use some sort of 
listener to identify when it goes out of scope (page expired etc), and 
then clean it up?

I wouldn't mind working on a patch, if I could get some pointers on 
where to start.

Thanks,
Jesse