Feature Request: Allow custom http headers to be rotated during the life of the client

[lot9s]

Describe the feature request

The use case I'm interested in was described well some years ago when a similar request was made for the .NET SDK: Unleash/unleash-dotnet-sdk#46

Solution suggestions

The solution that has been rolled out in the past for, e.g., the Node SDK and the Java SDK, was to add support for a customHeadersFunction or customHeadersProvider property when initializing an Unleash Client.

Would it be possible to provide support for something like that for the JS SDK, as well?

[gastonfournier]

Hi @lot9s, what type of headers would you like to rotate and why?
Because it's a frontend SDK, it's strange that you'd like to change the header in the middle of a user session. Would love to know about the use case, but other than that, I think it makes sense.
I think the idea is that you want to have short-lived frontend tokens. If you rotate them on the server side, you shouldn't need to change them dynamically in the client side, you can keep the old and new as valid until all clients are updated.
If you could propose a PR based on the solution in Node SDK we can have a look at it.