Merge branch 'proxy-headers' into 'develop'

MediaProxy RFC compliance

See merge request pleroma/pleroma!4062

changelog.d/content-length.fix

@@ -0,0 +1 @@
+MediaProxy was setting the content-length header which is not permitted by RFC9112§6.2 when we are chunking the reply as it conflicts with the existence of the transfer-encoding header.

lib/pleroma/reverse_proxy.ex

@@ -8,7 +8,7 @@ defmodule Pleroma.ReverseProxy do
                       ~w(if-unmodified-since if-none-match) ++ @range_headers
   @resp_cache_headers ~w(etag date last-modified)
   @keep_resp_headers @resp_cache_headers ++
-                       ~w(content-length content-type content-disposition content-encoding) ++
+                       ~w(content-type content-disposition content-encoding) ++
                        ~w(content-range accept-ranges vary)
   @default_cache_control_header "public, max-age=1209600"
   @valid_resp_codes [200, 206, 304]