option to include back path prefix

Can the issue be reproduced with the latest available release? y

Which one is the environment gotify server is running in?

[x] Docker
[ ] Linux machine
[ ] Windows machine
Docker startup command or config file here (please mask sensitive information)

Do you have an reverse proxy installed in front of gotify server? (Please select None if the problem can be reproduced without the presense of a reverse proxy)

[ ] None
[ ] Nginx
[ ] Apache
[x] Caddy
Reverse proxy configuration (please mask sensitive information)

[…]
  route /gotify/* {
    uri strip_prefix /gotify
    # Set the port to the one you are using in gotify
    reverse_proxy localhost:1245
  }
[…]

On which client do you experience problems? (Select as many as you can see)

[ ] WebUI
[ ] gotify-cli
[ ] Android Client
[x] 3rd-party API call (Please include your code)

What did you do?

curl -H "x-gotify-key: $token" 'https://example.com/gotify/message?limit=100&since=xxx'

What did you expect to see?

In the resulting JSON, next key points to https://example.com/gotify/message?limit=100&since=yyy

What did you see instead? (Include screenshots, android logcat/request dumps if possible)

Instead it points to https://example.com/message?limit=100&since=yyy losing the /gotify/ prefix.

The reverse-proxy configuration strips the prefix, so it's rather expected that gotify receives URLs without the prefix. So gotify should have an option to include that prefix when it emits URLs, like next.

gotify / server

option to include back path prefix #664