Add support for specifying base path

[JuniorJPDJ]

It would be great if while proxying, only routing by path would need to be applied. Adding base path to notify_push would solve that.

Why? For example: https://serverfault.com/a/336784

Example: add env var or cmdline argument to specify base path:

PUSH_BASE_PATH=https://your_nextcloud_address/push

After that you'd only need to route https://your_nextcloud_address/push/* to notify server in reverse proxy.

[icewind1991]

0a14040 doesn't cover this completely but should help with the common case without requiring extra configuration

[JuniorJPDJ]

It means it will just work with path starting with /push? Cool, I'm deploying then. Anyway would be cool to have base path implemented for more custom deployments, if you will not do this - just close ;D