Config.idFor() doesn't correctly handle multiple levels of nested anonymous structs

[phyrwork]

Description

Non-nil ID detection for @id tagged structure not working correctly with nested anonymous structs with more than one level

I have identified the bug and will submit a pull request with a fix

Steps to reproduce the issue:

type struct A {
  ID quad.IRI `quad:"@id"`
}

type struct B {
  A
}

type struct C {
  B
}

v := C{}
v.ID = quad.IRI("something") // Not-nil

rules, err := c.rulesFor(rt)
...
id, err := c.idFor(rules, rt, rv, "")
// id == nil

Received results:
See description

Expected results:

id = "<something>"

Output of cayley version or commit hash:

243214c801c26d9b36436ed3d92d4ed18298b309

Environment details:
n/a