It's not possible to add new XObjects of classes containing spaces in object mode

Steps to reproduce :

• Start with a clean instance
• Import the attached XAR package, it contains a simple AWM with 1 content page
• Edit the content page in object mode, try to add a new object of the "my test app" class

Expected : the object gets added
Actual : when refreshing the page, the object is not displayed anymore

This seems to come from the improvements performed as part of XWIKI-16210 : when a document is saved, we check if a request parameter addedObjects exists, and try to register the objects to add to the document.

In order to validate the contents of the request parameter addedObjects, we apply a regex XOBJECTS_REFERENCE_PATTERN, defined here ; the issue is that this pattern does not cover classes which have special characters (spaces, \, /, …) in their document name.

While it's a good practice to create class documents without special characters in their document names, it's certainly not the case always : for example, it's always possible to create an AWM with special characters.

This may also impact the pattern XPROPERTY_REFERENCE_PATTERN here.