[Deliverable] Extract RLN as a plug-in library from nwaku

[chair28980]

Owner: nwaku

Feature: Waku RLN API

FURPS:

• F1. Accepts RLN network configuration at initialization.

• F2. API to pass messages for proof validation.

• F3. API to import RLN credentials, compatible with RLN Membership management.

• F4. API to accept Waku Message and generate proof.

• F5. API to inform on configured rate limit parameters and remaining quota.

• U1. TWN RLN configuration is applied by default.

• U2. No boilerplate code beyond initialization is necessary to pass RLN instance in a Waku API implementation.

• U3. Rate usage is persisted across restarts.

• S1. library can be used in Go applications; available on pkg.go.dev.

• S2. library can be used in Rust applications; import via git path.

• S3. library can be used in Nim applications; import via git path.

• +1. Only one set of credentials can be used at a given t

Checklist:

• Specs: link to specs and/or API definition
• Code: link to GitHub issues/PRs/Epic
• Dogfood: link to dogfooding session/artefact
• Docs: links to README.md or docs.waku.org (TBD)