Coordinator service offchain support

[0xmad]

As a coordinator I'd like to use coordinator service for offchain message processing.

• [ ] Add rate limit for users to prevent spam
• [ ] Add api method for voting for user
• [ ] Add api method for user signup
• [ ] Coordinator can submit and recover from signature to verify its from the user
• [ ] Submit batch to IPFS every X votes
• [ ] Submit batch hash on chain
• [ ] Add seed phrase for coordinator service