IotDIR: rewrite identity provisioning

[oej]

2- Section 2, Identity provisioning: "... in some circumstances, a
manufacturer..." -> Could examples of these circumstances be added? For
instance, "examples include manufacturer-initiated key generation.

https://datatracker.ietf.org/doc/review-ietf-dance-architecture-06-iotdir-early-robles-2024-07-17/

[mcr]

"In some circumstances, a manufacturer may also publish device identity records in DNS.
In this case, the system integrator needs to perform network and application access configuration, since the identity already exists in DNS.
"

[mcr]

@oej, @shuque I don't really know what the circumstances are. When life is good?