### Check existing issues - [x] I've verified that this request isn't described by any existing issues. ### Request Streamline the process for preseeding images when building with Multipass. Currently, it requires users to export their signing key and import it with an override script. This approach also requires users to unlock the key in an interactive prompt, which resists automation. ### The problem it solves To preseed an image in a managed build, we currently have to export the key with: ``` gpg --homedir ~/.snap/gnupg --export-secret-keys <key-name> sign.key ``` and make it available in the build enviroment with something like: ``` parts: import-key: plugin: nil source: . override-build: | mkdir -p /home/ubuntu/.snap/gnupg chmod 700 /home/ubuntu/.snap/gnupg gpg --homedir /home/ubuntu/.snap/gnupg --import $CRAFT_PART_SRC/sign.key ``` A simpler method of preseeding in Multipass builds would be a nice improvement for users. At the very least, we should come up with a workflow for circumventing the interactive prompts.