Wrong URLs generated, when configured to use Traefik proxy

[martin5233]

Bug report

Expected Behavior

When clicking on any link in the UI, CDash should use the URL configured in APP_URL or MIX_URL

Actual Behavior

Configuration is as follows:
APP_URL=https://hostname/CDash3
MIX_APP_URL="${APP_URL}"

I have located two places, where this isn't the case:

• After a successful login the generated URL is wrong: http://hostname/projects
• Under MyCDash trying to create a new project generates the following URL: https://hostname/CDash3/project/CDash3/https://hostname/CDash3/projects/new

CDash Version

3.5.0rc3

Additional Information

storage/logs is empty, even though APP_DEBUG is set to true.
Traefik is configured as follows (if relevant at all):
- "com.docker.compose.project=cdash3"
- "traefik.http.middlewares.cdash3-stripprefix.stripprefix.prefixes=/CDash3"
- "traefik.http.routers.cdash3-ssl.entrypoints=webssl"
- "traefik.http.routers.cdash3-ssl.rule=PathPrefix(/CDash3)"
- "traefik.http.routers.cdash3-ssl.tls"
- "traefik.http.routers.cdash3-ssl.middlewares=cdash3-stripprefix@docker"
- "traefik.http.services.cdash3-ssl.loadbalancer.server.port=8080"
- "traefik.enable=true"