Ability to create route specific tags

[nicgirault]

With connect-datadog 0.0.9 it is not possible to add route specific tags. I would like to do so to associate routes to a SLO domain with a tag: domain:my-domain.

I don't see an elegant way to do so. One way would be to adjust this line to read tags that could have been added in middlewares defined after datadog middleware:

let statTags = [...tags, ...req.ddTags]

Would you merge such a PR?

[hybby]

Very interested in the feature proposed by #19 - could someone from Datadog confirm if there's any scope to merge this soon?