Allow for header based matching on the same path

[jonathan-whitaker]

In order to support matching based on headers or query params for the same path I had to change line 148 of
https://github.com/monimesl/istio-virtualservice-merger/blob/main/api/v1alpha1/virtualservicemerge_types.go

from:
targetRoutes = append(targetRoutes, pRoute)
to:
targetRoutes = append([]*v1alpha3.HTTPRoute{pRoute}, targetRoutes...)

This is because istio selects the first matching entry and since we have default services for the path and are matching headers for feature environments I needed the header matches to be listed first.

Not sure if you want this change as a PR but for now I've built my own image with the change and it is working for us.

[alphashaw]

Hello @jonathan-whitaker. We have been in your shoe.

I agree that the default implementation will have issues if a more generalized route is at then top of the list since istio chooses a route by doing sequential match testing.
However, since it's a list, I think appending new routes to the end seems more natural.

I have a proposal for us to have priority routes:
Can we have an optional -number suffix to the route name define in the patch that the operator can use to sort the VS route slice after adding new ones before updating?

[romanlum]

Any news here?
Is header matching with default route working?