Add url redirect

[hmueller01]

Add redirect function like ESPAsyncWebServer.
Sorry for the wrong commits/reverts. Obviously my master wasn't clean.

[hmueller01]

Is it possible to merge this, also there is a build problem on Linux? Seems to be not the fault of this PR ...

[d-a-v]

What about using this API in our examples ?

[hmueller01]

@d-a-v Sorry, but I do not understand your comment. These are examples that do a redirect. My proposal was to add this out-of-the-box of the ESP8266WebServer ...

[d-a-v]

Sorry for lack of clarity.
You added a new API.
I propose you to update our examples to use it.
They would become examples of how to use your new API, examples are meant for that.
Lots of users take them as basis to start their project.
My link above shows you where you could make these changes.

[hmueller01]

Oh, sry for being so stupid. Sure, I'll do this in the next few days.

[hmueller01]

Looking through the examples I found this:

  server.send(302, "text/plain", "");  // Empty content inhibits Content-length header so we have to close the socket ourselves.
  server.client().stop();  // Stop is needed because we sent no content length

Why is it needed to stop the client? Should this be done in redirect() as well, if I do not send content?

[d-a-v]

Why is it needed to stop the client? Should this be done in redirect() as well, if I do not send content?

It seems to be a good idea.

[hmueller01]

@d-a-v Ok, I finished my work on this. Also did some tests and it looks good.
Damn it. Just saw some checks are failed. Will fix this first ...

[hmueller01]

Fixed. All checks have passed. 👍

[hmueller01]

I just merged with master and it still looks clean.
@d-a-v Is this ready form merging now (and adding to a new release you just mentioned)?