Can't define PortableCommandAlias when creating a nested installer

[taki-eddine-47]

Describe the bug:
When creating a zip package, winget gives the two options for NestedInstallerFiles, RelativeFilePath and PortableCommandAlias, wingetty doesn't provide the second option.

Example: https://github.com/microsoft/winget-pkgs/blob/master/manifests/s/Stenzek/DuckStation/0.1.6280/Stenzek.DuckStation.installer.yaml

To Reproduce:
Steps to reproduce the behavior:

Expected behavior:
Ability to define PortableCommandAlias.

Screenshots

General Information:

• OS: Docker
• Browser: any
• WinGetty: 1.0.0

Additional context:
Just quick search in code.
In the form, you can find only use of RelativeFilePath: https://github.com/thilojaeggi/WinGetty/blob/115adecb9b6b7afd6c56bb29e82126ef0adb2a78/app/forms.py#L108C40-L108C61
But the model support the second option:

WinGetty/app/models.py

Line 130 in 115adec

"PortableCommandAlias": nested_installer_file.portable_command_alias,