services/fs: Proposal: Support file permission and owner

[Xuanwo]

We could introduce file permission and owner support via add new service pair and metadata.

Proposal

Pair

permission could be set in open, but uid/gid may need a call to Chown.

• permission: uint32, The permission of this object (for Write related operation)
• uid: uint32, The uid of this object
• gid: uint32, The gid of this object

Metadata

We could extract following metadata from f.Sys().(*syscall.Stat_t) (unix only)

• permission: uint32, The permission of this object
• uid: uint32, The uid of this object
• gid: uint32, The gid of this object

Retional

• How to support permission control on windows? As windows have different concepts compared to Unix alike system.
  • we could just ignore the support for windows for now.