Add memo field

[adizere]

Crate

ibc-relayer-cli

Summary

We'd like to allow the parametrization of the memo for transactions that Hermes submits.

Proposal

There should be two parts to this memo:

1. a user-configurable part of the memo, e.g., "relayed by operator X"

   • this will serve as a prefix to the overall memo field
   • should be parametrizable on a per-chain basis from the config.toml
   • consider a domain-type validation to hard-limit the allowed length of this field, probably 100 chars

2. a fixed string representing the Hermes build version plus a link to https://hermes.informal.systems

An example of a memo would be this:

relayed by operator x | Hermes v0.7.3 https://hermes.informal.systems

Acceptance Criteria

• the memo field in tx submitted by Hermes reflects the user-configurable prefix as well as the Hermes version and website

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