grouping inline-or-keystore-symmetric-key-grouping:
    +-- (inline-or-keystore)
       +--:(inline) {inline-definitions-supported}?
       |  +-- inline-definition
       |     +---u ct:symmetric-key-grouping
       +--:(central-keystore)
                {central-keystore-supported,symmetric-keys}?
          +-- central-keystore-reference?
                  ks:central-symmetric-key-ref