Custom Headers: basic implementation

[Dopingus]

This is a very basic implementation of custom headers as described in #326.
Unfortunately, I do not really do UI programming or mobile app programming at all so the UI for adding new headers does not work at all.
I need some help to make this PR work e2e.

Manually setting the headers by providing an array of strings with the format "HEADER_NAME=HEADER_VALUE" successfully bypasses Cloudflare, so I can actually reach my Subsonic/Ampache instance with hardcoded headers.

[BLeeEZ]

Thank you for providing this proof of concept.
I have some loose ends that I need to complete first. I currently don't know when I have time to complete this.
Points to be done:

• Create UI for login screen in UIKit.
• Save the header configuration persistent in the PersistentStorage
• Add an additional screen to the config:
  1. display the current applied headers
  2. change/delete the header configuration

[Jerra94]

I'm interested in this feature as well so that I can securely access my server from anywhere without vpn.

[YJCHOO]

Any update for this enhancement ?

[WildeTechSolutions]

Also curious if there's been an update. This is a vital feature for proxy authentication, and as OP mentioned, this is offered by Symfonium over on Android.