Publish generated proto clients in an idiomatic way

[znewman01]

When writing a client library for Sigstore, you'll need access to the protos. Manually copying them in is tedious and error-prone.

Instead, we should publish sigstore-protos libraries in a language-idiomatic way (e.g., on a popular package repository).

The languages that will need this:

• Ruby (RubyGems)
• Java (Maven Central) Add release build for java #33 Add release script #43 Create and publish new java release v0.0.1 #45
• JavaScript (npm)
• Go? (Go just uses Git but I'm not sure how it works with generated files).
• Rust (Cargo)
• Python (PyPI) Generate Python bindings? #20 Automatic Python release workflow #32 Fix Python release workflow (hopefully) #34 Fix Python release, take 2. #35

We'll probably want advice from representatives of each community, since no maintainer on this repo understands best practices for all of these languages unless somebody has weird hobbies they're not telling me about.

[vlsi]

Java (Maven Central)

+1

[kommendorkapten]

You are one step ahead of me @znewman01, like it!

For go my plan is that we generate the go code in this repository as part of a CI job, this is a pattern I'm used to and it works well.
I will also work with the secure systems lab to do the same for the DSSE code so we don't need to replicate that code generation here.