Redirect from index-page should not replace protocol

[mfriedenhagen]

Describe the bug
I start plantuml in Kubernetes and have Traefik as SSL offloaded in front of it.
When I just navigate to the "entry page" I get redirected but the protocol is changed from https to http
Because I do not expose the http interface in Traefik I get a 404

To Reproduce
Steps to reproduce the behavior:

❯ curl -i https://plantuml.example.com
HTTP/2 302 
location: http://plantuml.example.com/uml/SyfFKj2rKt3CoKnELR1Io4ZDoSa70000
server: Jetty(11.0.18)
content-length: 0
date: Wed, 29 Jan 2025 13:55:48 GMT

❯ curl -i https://plantuml.example.com/
HTTP/2 302 
location: http://plantuml.example.com/uml/SyfFKj2rKt3CoKnELR1Io4ZDoSa70000
server: Jetty(11.0.18)
content-length: 0
date: Wed, 29 Jan 2025 13:55:53 GMT

Expected behavior

• The redirect picks up the protocol and I will be redirected to https://plantuml.example.com/uml/SyfFKj2rKt3CoKnELR1Io4ZDoSa70000

Desktop (please complete the following information):

• It do not think these are relevant.

Similar to https://support.oracle.com/knowledge/Middleware/3013718_1.html

[arnaudroques]

Thanks for the report.

However, this issue should be opened on https://github.com/plantuml/plantuml-server