StringToRole takes role string case insensitive and returns a GUEST role if no role was found with the provided string.

example: f235122f9a1e4884123456788a2126f8dd76996b.

Unset/Zero value Role = 0.

Permission holds an byte slice for the pattern --/rw or ----/r-r- and so on none read write 0 == - | 1 == r | 2 == w to support []byte we implement the json marshaller interface otherwise use []int.