Convos does not work properly behind reverse proxy with path

[gschwind]

Describe the bug
When convos is behind a reverse proxy with a path such as https://dnsname.com/convos, Convos does not work properly.

After investigating, several URL used in the web interface does not have the path. For instance:

convos request https://dnsname.com/api , where it should be https://dnsname.com/convos/api, I guess

To Reproduce

1. Setup apache with:

   # Enable Convos to construct correct URLs by passing on custom headers.
   ProxyRequests Off
   ProxyPreserveHost On
   
   RequestHeader set X-Request-Base "https://dnsname.com/convos"
   
   # https://httpd.apache.org/docs/current/mod/mod_remoteip.html
   RemoteIPHeader X-Forwarded-For
   
   # http://httpd.apache.org/docs/2.0/mod/core.html#limitrequestbody
   LimitRequestBody 0
   
   # Pass requests on to Convos
   ProxyPass /convos/events ws://localhost:3001/events
   ProxyPass /convos/ http://localhost:3001/ keepalive=On
   ProxyPassReverse /convos/ http://localhost:3001/convos/
   

2. start convos with:

   CONVOS_REQUEST_BASE="https://dnsname.com/convos/" CONVOS_REVERSE_PROXY=1 ./script/convos daemon --listen http://127.0.0.1:3001

3. Open https://dnsname.com/convos

Convos show the login dialog but is partially loaded and does not work properly. Several HTTP resources aren't loaded and several HTTP request fail.

Expected behavior
Convos load all resource properly and can be used under a given http path

Environment:

• OS: Linux/Debian on aarch64
• Browser firefox on Linux/amd64
• Version 140.10.1esr
• IRC none (cannot login)