[BUG] service parameter missing in AwsSigv4SignerOptions

[nand-biz4group]

interface AwsSigv4SignerOptions {
getCredentials?: () => Promise;
region: string;
service?:string;
}
Because it is required in opensearch serverless

[gauravbiz4group]

I think it's already resolved in GitHub repo code:

but not updated on the npm package:

[dblock]

Fixed in #377 already, but please double-check @nand-biz4group that the version on HEAD works for you? We need to release 2.3, add your +1 to #303 please.