Reference the deploying users originating Public IP Address

I am deploying a KeyVault, with public access denied and want to easily add my Public IP Address to the Keyvault Allow List.

In order to do this I add a parameter to the bicep, but I am reliant on the deploying user knowing their public ip address and passing the correct parameter value with the correct cidr notation.

It would be much cleaner if I could reference this within bicep itself, eg;

```bicep
param keyvaultAllowIP string = deployment().initiator.originatingIP
```

Start by tracing how the deployment() function exposes deployment metadata and whether Azure provides the deploying user's originating public IP. Check the Key Vault allow-list scenario and the proposed deployment().initiator.originatingIP expression. Done means establishing a supported way to reference the address, or documenting the limitation if that data is unavailable.

Written by the indexing model from the issue text.