Custom request headers validation not working - fails silently

[Root-Core]

Describe the Bug

As described here: #3172 (comment)
I moved this here, as this is a separate issue and not specific to this PR.

A failed client side validation is not presented to the user and the saving process isn't blocked, but the new data is not send to the server. The previous, last known good settings are.

Environment

• OS Type & Version: Debian 13
• Pangolin Version: 1.19.4
• Edition (Community or Enterprise): Enterprise

To Reproduce

1. Navigate: Network > Public > Edit > HTTP Settings > Additional Proxy Settings > Custom Request Headers
2. Add x-test: test
3. Save (should work)
4. Add not_valid
5. Save (should not work)

You get a "Settings successfully updated", but the client sends the old x-test: test to the server.
This indicates, that the client side validation silently fails and the server side validation is never triggered.

Expected Behavior

There should be an error message while trying to save or an inline validation error beforehand.

[AstralDestiny]

Poked the rest.

[Root-Core]

Poked the rest.

What do you mean? Could you elaborate?