[video_player]add http headers option when loading network data source

[rcunning]

I added optional request headers to VideoPlayerController.network contructor for video_player plugin. I did not see an obvious place to create a test for these changes, but happy to do so if you would like. I did manually test these changes on iOS and Android emulator.

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[rcunning]

I signed it!

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[cbenhagen]

Hi, thank you for trying to finally fix flutter/flutter#16466. There is already a very similar PR open here #897.

The problem seems to be the usage of AVURLAssetHTTPHeaderFieldsKey. I can't tell if the usage of this private API would really get an app rejected. Can you try to get more information on this?

[ezamagni]

I really need this feature for my project. Unfortunately this PR seems abandoned. Any chance in getting it resumed?

[rcunning]

I really need this feature for my project. Unfortunately this PR seems abandoned. Any chance in getting it resumed?

See comments in feature request flutter/flutter#16466 and a similar pr #897

If I were you and you really need it, fork the repo, apply one of the prs (will have to update a little I am sure), and move on. You will have to merge in changes from the main repo though whenever you want the latest (see https://help.github.com/en/github/collaborating-with-issues-and-pull-requests/merging-an-upstream-repository-into-your-fork).

[troyanskiy]

Can someone resolve the conflicts and merge it. That is very useful feature!
Thank you!

[stuartmorgan]

Closing, as there is already #897 which addresses the same issue; let's consolidate discussion there.