Discussion: Is it OK to not support previous VerifyingKey versions?

[ed255]

From here:

halo2/halo2_proofs/src/plonk.rs

Line 123 in 73408a1

if VERSION != version_byte[0] {

In halo2, whenever an update changes the VeriyingKey type in a non forward-compatible manner we're supposed to bump the version. When reading a serialized VerifyingKey, older versions are rejected.

I think supporting multiple versions could add a lot of complexity, but we can discuss this.

Discussion from #254 (comment)