Update publications + documentation high level sites

• Publications ( https://hifis.net/documentation ):
  • nfdi pres marcus
  • paper osn
  • dfn paper: check updates in https://www.dfn.de/publikationen/dfnmitteilungen/

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• Documentation ( https://hifis.net/publications )
  • aai / policies
  • aai / doc
  • aai concept
  • cloud services doc
  • backbone core services doc
  • service usage git