Bug: permission model outdated

[maurictg]

Hi! According to the recent docs the permissions are now stored as following:

Related code fragment: https://github.com/plabble/ptpd/blob/main/store/bucket.go#L82

Byte 15 of BucketId

bit 0: random
bit 1: random
bit 2: public read
bit 3: public write
bit 4: public append
( private read is always true, so not stored anymore )
bit 5: private write
bit 6: private append
bit 7: allow bucket to be deleted

I would suggest:

type BucketPermissions struct {
	Read   bool
	Write  bool
	Append bool
        DeleteBucket bool
}

// ...

if authorized {
		return BucketPermissions{
			Read:   true,
			Write:  id[15]&8 != 0 || id[15]&32 != 0,
			Append: id[15]&16 != 0 || id[15]&64 != 0,
                        DeleteBucket: id[15]&128
		}
	} else {
		return BucketPermissions{
			Read:   id[15]&4 != 0,
			Write:  id[15]&8 != 0,
			Append: id[15]&16 != 0,
                        DeleteBucket: false
		}
}