[Feature Request] Fill in user's Azure object id by default

- If the issue is to do with Azure CLI 2.0 in-particular, create an issue here at [Azure/azure-cli](https://github.com/Azure/azure-cli/issues)

### Extension name (the extension in question)
Healthcareapis

### Description of issue (in as much detail as possible)
Currently a user needs to find and manually enter their Azure object id as their Access Policies Object Id when creating a service. It would be convenient to have the object id be automatically retrieved by the extension and provided as a default value if the user didn't enter a value.
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