How can I sign a Debian package created from rust project?

Question

I need to sign the .deb file I'm creating using cargo deb. So either:

• How do create the .changes file from an existing .deb file? (cargo deb doesn't seem to do that). Or,
• How do I use debcargo for a project that is only local and not on https://crates.io?

At the end of the day I want to host our own apt repository and I need to have signed packages to do that it.