feat: move CERN-specific config section from diracx to lhcbdiracx
There was a TODO in the diracx UserConfig section, so here you go:
https://github.com/DIRACGrid/diracx/blob/c265a47363850662502bb7f0fb8ebbbe94893e85/diracx-core/src/diracx/core/config/schema.py#L75-L81
IIUC, we won't be the only community to use these fields right? I guess it's ok at the moment if we duplicate these fields in our extensions, but we might keep this in mind if we have more CERN-specific config/agents/services to share in the future.