feat: Replace $http_host in nginx.conf, add support for proxies

When using a reverse proxy in front of the application,
`$http_host` might point to an network internal address.
The `proxy_redirect` response points to the internal address then,
which leads to redirects to internal addresses (failing requests).

helm/config/nginx.conf

@@ -25,8 +25,8 @@ http {
         location /api/v1/ {
             client_max_body_size 30m;
             proxy_pass http://{{ .Release.Name }}-backend:80;
-            proxy_redirect http://{{ .Release.Name }}-backend {{ .Values.general.scheme }}://$http_host;
-            proxy_redirect http://{{ .Release.Name }}-backend:80 {{ .Values.general.scheme }}://$http_host;
+            proxy_redirect http://{{ .Release.Name }}-backend {{ .Values.general.scheme }}://{{ .Values.general.host }}:{{ .Values.general.port }};
++           proxy_redirect http://{{ .Release.Name }}-backend:80 {{ .Values.general.scheme }}://{{ .Values.general.host }}:{{ .Values.general.port }};
         }
     }
 }