C++, allow the creation of link anchors to deal with namespaces in parameters' types

Problem description

When I describe a class or struct with .. cpp:class:: I like to give the full namespace qualification. But when I use this class as a parameter type in .. cpp:function:: or as type in .. cpp:var::, I prefer to keep it clear and lightweighted. As a result, the links from the parameters to their types are broken.

My logs are full of such error message:

docstring of simgrid::s4u::VirtualMachine::on_resume:1: WARNING: cpp:identifier reference target not found: xbt::signal<void(VirtualMachine const&)>

(Here, the problem seems to come from the fact that the xbt::signal template is used on the partially qualified VirtualMachine type name while the documented name is the full simgrid::s4u::VirtualMachine)

Solution I'd like
Since I'm using the cpp domain almost directly, I'd like to have a manual solution at hand, such as a .. cpp:anchor or something that would allow me to write something as follows:

.. cpp:anchor:: VirtualMachine

   (no parameter nor content here)

.. cpp:class:: simgrid::s4u::VirtualMachine

   (class description here)

.. cpp:var:: xbt::signal< void(VirtualMachine const  &)> simgrid::s4u::VirtualMachine::on_resume

   (variable description here)

Alternative I've considered

I've considered qualifying all types in parameters and such, but this leads to very heavy rendering in the doc. I think that this greatly hinders the doc readability.

Additional context

• My project is https://simgrid.org.
• The online documentation is here: https://simgrid.frama.io/doc/latest/app_s4u.html#api-reference
• It's built in the CI of the https://framagit.org/simgrid/simgrid project
• I'm using a set of sphinx extension of my own to extract the doc from Doxygen, but I don't think it's related here.

Start by tracing the C++ domain entries for cpp:class, cpp:function, and cpp:var and how they resolve identifiers. Add a manual anchor mechanism that makes the partially qualified parameter type resolve to the documented class, then add regression coverage showing the example links without requiring fully qualified parameter types.