Creating local user with public key failed to validate key

### Related command
```bash
az storage account local-user create --account-name accname -g private_rg -n sftpuser --home-directory sftp --permission-scope permissions=rwlcd service=blob resource-name=sftp --ssh-authorized-key key="*SSH_KEY*" --has-ssh-key true
```

### Extension name
storage-preview

### Description of issue
When supplying the contents of a rsa `.pub` file to the `key` property, I get the below error.
I did notice the trailing `=` seem to get dropped in the output not sure if they are maybe getting dropped on input.
Error:
```
Code: InvalidBase64String
Message: String AAAAB3Nza...g04Dyy6Iw is not base64 encoded.
```

I've also tried base64 encoding the contents on the rsa `.pub` file and supplying that in the key data section but that results in the same error.

Key was generated using `ssh-keygen -m PEM -t rsa -b 4096 -f ./keyfile`

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OS: macOS Monterey - 12.3.1 (21E258)
Shell: ZSH