New chain connector: Cosmos

[kmw101]

Add a new chain connector to support Cosmos.

MVP: support Cosmos Hub and ATOM (we can generalise to other chains/tokens at a later point). We should be able to reuse our Tendermint code.

• Research which transaction types we want to support
• Test setup of Cosmos Hub node (https://hub.cosmos.network/docs/deploy-testnet.html)
• Start Cosmos node in Travis
• @iov/cosmos package setup
• Encoding/decoding
• Codec
• Connection [MVP]
• Connector

[willclarktech]

Based on modules listed here: https://github.com/cosmos/gaia/blob/master/docs/what-is-gaia.md

Transactions to include:

• bank/send: https://github.com/cosmos/cosmos-sdk/blob/master/x/bank/internal/types/msgs.go#L10-L15

Transactions to exclude:

• bank/multisend: https://github.com/cosmos/cosmos-sdk/blob/master/x/bank/internal/types/msgs.go#L57-L61
• staking/*: https://github.com/cosmos/cosmos-sdk/blob/master/x/staking/handler.go#L16-L41
• distribution/*: https://github.com/cosmos/cosmos-sdk/blob/master/x/distribution/handler.go#L12-L31
• slashing/*: https://github.com/cosmos/cosmos-sdk/blob/master/x/slashing/handler.go#L10-L24
• gov/*: https://github.com/cosmos/cosmos-sdk/blob/master/x/gov/handler.go#L10-L30

[willclarktech]

@webmaster128 Under which version should CHANGELOG entries appear?

[webmaster128]

@webmaster128 Under which version should CHANGELOG entries appear?

I suggest collecting them at an extra place (here, wiki, private notes, Confluence, gist) and add them to the first release that publishes a @iov/cosmos package.

[willclarktech]

@webmaster128 OK to close this issue and open follow-ups for improvements eg RPC support?

[webmaster128]

👍 We just need to create an overview of what is missing before we can un-private @iov/cosmos. Using the chain IDs from ChainAgnostic/CAIPs#5 is one open thing. Balance subscriptions would be needed for wallet integration.