Add custom HTTP header support for proxies

[markrosan8]

Description

Adds a "Custom HTTP Header" settings section in the Settings page with two text fields for a header name and value. Values are saved to UserDefaults.standard and read by the SDK's prepareRequestForScheduling: to attach the header to every outgoing request.

Companion PR: opencloud-eu/ios-sdk#6

Related Issue

Resolves https://github.com/orgs/opencloud-eu/discussions/2557

Motivation and Context

Users running OpenCloud behind reverse proxies sometimes need a custom HTTP header on all requests for routing or authentication gating. The iOS app currently has no way to attach custom headers, which can prevent the app from working in these deployments.

How Has This Been Tested?

Built and tested on iOS sim. Verified via Traefik access logs that the custom header appears on all outgoing requests. Verified that leaving the fields empty results in no change to existing behavior.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• Added an issue with details about all relevant changes in the docs repository.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have set a pull request label and a meaningful title for changelog automation

[markrosan8]

If this is approved, I can submit similar PRs for the other clients as necessary.

[markrosan8]

@kulmann @guruz Hello, any updates on this?

[guruz]

Thank you for the PR. I have no opinion on this yet (and of course we could merge it if the code is OK) but I'd want to know what others think (that have more clue than me) about the general idea of having https://github.com/orgs/opencloud-eu/discussions/2557 .
@micbar @butonic @rhafer ?

[guruz]

By the way, in theory this should be a property of the account (since it's a multi account app) and not a global app setting!

Hmmmm. But that's harder to integrate UI wise.

@micbar @butonic @rhafer Can't this also be something the IDP tells the app?

[markrosan8]

@guruz thanks for taking a look. You’re right in theory this should be account level, and I did in fact consider that when writing. But it would have been more complex, for what I saw to be minimal benefit. I assume the number of people using edge auth on two accounts simultaneously is very low (probably the number of people using two opencloud accounts itself is low).

And either way, no one is able to use edge auth with iOS currently. So it’s not a regression in my view. But, let me know your thoughts.

[markrosan8]

It would be useful to note this restriction in the footer, if we choose to implement.

[guruz]

I have an idea for an UI that would help both you and @paolostivanin .. I'll post it to https://github.com/orgs/opencloud-eu/discussions/2557 tomorrow.