identity: Allow identities with all null attributes to change #1228
Description
Module version
v1.16.0
Context
Similar to an SDKv2 issue that was raised and fixed: hashicorp/terraform-plugin-sdk#1527
While we want to prevent identities from being stored with all null values or null (#1184), it currently is possible for this to be in state via older versions of Terraform / SDKv2 / Framework (or custom terraform-plugin-go implementations). An identity with all null attributes is equivalent to an identity that is null, so we should prevent change validation from running in that scenario (the latter we already ignore during change validation).
Adjacent but different to: #1193