framework: support for nginx reverse proxy

[ymartin59]

Document and write an example in demoservice package to create a publication alias in DSM nginx to publish a service running on its custom port

[publicarray]

Afaik everything is done by the user: https://kb.synology.com/en-ca/DSM/help/DSM/AdminCenter/system_login_portal_advanced?version=7

[hgy59]

Since DSM 7.0 it is possible to configure a reverse proxy for packages. Example from developer guide:

reverse_proxy service worker setting example:

{
   "service": "gitlab",
   "display_name": "Git Lab",
   "support_alias": true,
   "support_server": true,
   "type": "reverse_proxy",
   "icon": "ui/gitlab_{0}.png",
   "proxy_target": "http://gitlab:30000",
   "proxy_headers": [{
   "name": "host",
   "value": "gitlab"
   },{
   "name": "Upgrade",
   "value": "$http_upgrade"
   },{
   "name": "Connection",
   "value": "$connection_upgrade"
   }]
   "connect_timeout": 60,
   "read_timeout": 3600,
   "send_timeout": 60
}

[hgy59]

@ymartin59 I tried to create a reverse proxy for the new demowebservice package in #5649

I added the following code to the resource file, but it did not create a reverse proxy (package installation on DSM 7 did succeed without any error)

         {
            "service": "demowebserviceproxy",
            "display_name": "Demo Web Service Proxy",
            "icon": "app/images/demowebservice-{0}.png",
            "type": "reverse_proxy",
            "proxy_target": "http://localhost:8889",
         }

Manual creation of a reverse proxy works as expected. And the system created/updated the reverse proxy config file /usr/syno/etc/www/ReverseProxy.json The entry for the demowebservice looks like

        "e6c61973-83e4-4ca2-a132-b9ab56357301" :
        {
                "backend" :
                {
                        "fqdn" : "localhost",
                        "port" : 8889,
                        "protocol" : 0
                },
                "customize_headers" : [],
                "description" : "Demo Web Service Proxy",
                "frontend" :
                {
                        "acl" : null,
                        "fqdn" : null,
                        "https" :
                        {
                                "hsts" : false
                        },
                        "port" : 8443,
                        "protocol" : 1
                },
                "proxy_connect_timeout" : 60,
                "proxy_http_version" : 1,
                "proxy_intercept_errors" : false,
                "proxy_read_timeout" : 60,
                "proxy_send_timeout" : 60
        },

Since there are no properties for the source (frontend) of a reverse proxy documented in the DSM 7 Developer Guide by Synology, I suppose that either the documentation is incomplete or it is not possible to create a "reverse_proxy" service.