Support Helper Function Calls in Form Configuration

[dwisiswant0]

# $HOME/.config/katana/form-config.yaml
name: "{{rand_first_name()}} {{rand_last_name()}}"
email: "{{rand_email()}}"
phone: "{{rand_phone()}}"
address: "{{rand_address()}}"
cc: "{{rand_credit_card()}}"
password: "{{rand_password()}}"

[github-actions]

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