Make `epoch` non optional in `RegisterSignerMessage`

[jpraynaud]

Why

The epoch field of the RegisterSignerMessage is optional but sent by all the signers from distribution 2318. We want to make it non optional.

Note

The signer version released with 2318 distribution is 0.2.36 which is not run any more by any signer in the release-mainnet network. Thus it is not considered as a breaking-change.

What

Make the epoch field non optional in RegisterSignerMessage (marked by era_deprecate!("make epoch of RegisterSignerMessage not optional"); in the code.

How

• Make the epoch field non optional in RegisterSignerMessage
• Update the patch version of the Open API specification