web-provider: only active configuration fetched for the current context

[andreas-karlsson]

Expected behavior

When a new configuration is fetched it should only become active if the context it was fetched for, is (still) the current context when the fetch is resolved.

Actual behavior

If the context is changed in rapid succession we have a race condition. If the fetches don't resolve in the same order they were started, we might activate the "wrong" configuration.

See for instance here. Note: The same problem is applicable to initialise followed by a context change.

[Billlynch]

Note, this only makes sense in the static paradigm of OpenFeature, so the issue is only scoped to the web provider. IMO.