Merge branch 'docs/storing-remote-media' into 'develop'

Document how to store remote media permanently

See merge request pleroma/pleroma!1871

docs/configuration/storing_remote_media.md

@@ -0,0 +1,38 @@
+# Storing Remote Media
+
+Pleroma does not store remote/federated media by default. The best way to achieve this is to change Nginx to keep its reverse proxy cache
+for a year and to activate the `MediaProxyWarmingPolicy` MRF policy in Pleroma which will automatically fetch all media through the proxy
+as soon as the post is received by your instance.
+
+## Nginx
+
+```
+    proxy_cache_path /long/term/storage/path/pleroma-media-cache levels=1:2
+        keys_zone=pleroma_media_cache:10m inactive=1y use_temp_path=off;
+
+    location ~ ^/(media|proxy) {
+        proxy_cache        pleroma_media_cache;
+        slice              1m;
+        proxy_cache_key    $host$uri$is_args$args$slice_range;
+        proxy_set_header   Range $slice_range;
+        proxy_http_version 1.1;
+        proxy_cache_valid  206 301 302 304 1h;
+        proxy_cache_valid  200 1y;
+        proxy_cache_use_stale error timeout invalid_header updating;
+        proxy_ignore_client_abort on;
+        proxy_buffering    on;
+        chunked_transfer_encoding on;
+        proxy_ignore_headers Cache-Control Expires;
+        proxy_hide_header  Cache-Control Expires;
+        proxy_pass         http://127.0.0.1:4000;
+    }
+```
+
+## Pleroma
+
+Add to your `prod.secret.exs`:
+
+```
+config :pleroma, :instance,
+  rewrite_policy: [Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy]
+```