[Enhancement] Allow IPv6 (#372)

* Added option to enable IPv6 in runtime config

* Updated README

README.md

@@ -151,7 +151,8 @@ If you change this setting and it works well for you, please leave a comment on
 | `LOG_LEVEL`                 | No        | `debug`                   | Can be set to `info` but `debug` is strongly recommended                                                                        |
 | `BASIC_AUTH_USERNAME`       | No        |                           | See [authentication docs](https://github.com/kieraneglin/pinchflat/wiki/Username-and-Password)                                  |
 | `BASIC_AUTH_PASSWORD`       | No        |                           | See [authentication docs](https://github.com/kieraneglin/pinchflat/wiki/Username-and-Password)                                  |
-| `EXPOSE_FEED_ENDPOINTS`     | No        |                           | See [RSS feed docs](https://github.com/kieraneglin/pinchflat/wiki/Podcast-RSS-Feeds)                                            |
+| `EXPOSE_FEED_ENDPOINTS`     | No        | `false`                   | See [RSS feed docs](https://github.com/kieraneglin/pinchflat/wiki/Podcast-RSS-Feeds)                                            |
+| `ENABLE_IPV6`               | No        | `false`                   | Setting to _any_ non-blank value will enable IPv6                                                                               |
 | `JOURNAL_MODE`              | No        | `wal`                     | Set to `delete` if your config directory is stored on a network share (not recommended)                                         |
 | `TZ_DATA_DIR`               | No        | `/etc/elixir_tzdata_data` | The container path where the timezone database is stored                                                                        |
 | `BASE_ROUTE_PATH`           | No        | `/`                       | The base path for route generation. Useful when running behind certain reverse proxies                                          |

config/runtime.exs

@@ -66,6 +66,7 @@ if config_env() == :prod do
   journal_mode = String.to_existing_atom(System.get_env("JOURNAL_MODE", "wal"))
   # For running PF in a subdirectory via a reverse proxy
   base_route_path = System.get_env("BASE_ROUTE_PATH", "/")
+  enable_ipv6 = String.length(System.get_env("ENABLE_IPV6", "")) > 0
 
   config :logger, level: String.to_existing_atom(System.get_env("LOG_LEVEL", "debug"))
 
@@ -120,7 +121,7 @@ if config_env() == :prod do
       # Set it to  {0, 0, 0, 0, 0, 0, 0, 1} for local network only access.
       # See the documentation on https://hexdocs.pm/plug_cowboy/Plug.Cowboy.html
       # for details about using IPv6 vs IPv4 and loopback vs public addresses.
-      ip: {0, 0, 0, 0},
+      ip: if(enable_ipv6, do: {0, 0, 0, 0}, else: {0, 0, 0, 0, 0, 0, 0, 0}),
       port: String.to_integer(System.get_env("PORT") || "4000")
     ],
     url: [path: base_route_path],