Explore alternative ways of generating metadata

[untitaker]

Currently we have a few problems:

1. Exporting metadata through the .h file is nice (because it uses existing setup) but quite a hack.
2. Keeping Python "client" library and Rust "server" library in sync is rather hard until shippai hits 1.0 -- you can pin the version in Cargo, but not really in Python
3. Python dependencies still have high cost

Ideas:

• re 1 + 3: Generate Python wrapper from Rust code, let user check in Python wrapper
• re 2: Just stabilize shippai to 1.0 and never change a thing ever