we also want to bump this value in package-lock.json

the best way to handle this is, before manually changing any version numbers, run

npm version minor from modules/chronik-client

this will update package.json and package-lock.json

was this file generated by npm run build-proto ?

imo the API would be improved if the coinbaseData key were omitted for cases where it is undefined

this is how chronik-client handles other keys that are defined/undefined in some cases.

To do this, need to build this onMessage object -- then conditionally add the coinbaseData key if it is present.

See for example the convertToTx function in this file, which only includes block if the tx is confirmed.

mb redundant to use coinbaseOutputs and coinbaseScriptsig inside CoinbaseData?

why not

export interface CoinbaseData {
   scriptsig: string;
   outputs: TxOutput[];
}

not a blocker