homebase-lite-backend: Backend for onchain proposal title

[EightRice]

Since there's no Title field in the contract, we should save the title of the onchain proposal in the Lite mongodb instace.

(For reference, here is the frontend task for this: https://app.zenhub.com/workspaces/tezos-homebase-63238426ddf385159a4c4b12/issues/gh/dorgtech/homebase-app/722 )

[EightRice]

Hey team! Please add your planning poker estimate with Zenhub @EightRice @Man-Jain

[benefacto]

I'd like to get #738 merged before diving into this one as I'll be building on that foundation