building-multi-agent-system problem with import a2a_card_dispatch function

[Vadiml1024]

There is a problem with with agent code trying to import
a2a_card_dispatch function from a2a_utils.py. The function is absent in the a2a_utils.py file provided in agent subdirs.
the solution is to add this function to the file and move it to shared directory and have symlinks to the shared version in the subdirs.
The same should be dont adk_app.py and authenticated_httpx.py file.

[vladkol]

@Vadiml1024 I looked into agents subdirectory. Each agent has a symlink to the implementation in shared directory.