[ruby/open-uri] Add `request_specific_fields` option for customizing headers

This commit introduces the `request_specific_fields` option in OpenURI.
It provides two methods for customizing headers as follows.

1. Specify headers only for the initial request

Use a Hash to apply headers only to the first request.
These headers are automatically removed during redirects.

2. Specify headers dynamically for each request

Use a Proc to dynamically generate headers for each request,
including during redirects, based on the request URL.

This feature allows users to control headers flexibly,
ensuring that sensitive headers like "Authorization" are not unintentionally
transferred during redirects unless explicitly specified.

https://github.com/ruby/open-uri/commit/460f858e3c

lib/open-uri.rb

@@ -109,6 +109,7 @@ module OpenURI
     :redirect => true,
     :encoding => nil,
     :max_redirects => 64,
+    :request_specific_fields => nil,
   }
 
   def OpenURI.check_options(options) # :nodoc:
@@ -148,7 +149,11 @@ module OpenURI
       end
       encoding = Encoding.find(options[:encoding])
     end
-
+    if options.has_key? :request_specific_fields
+      if !(options[:request_specific_fields].is_a?(Hash) || options[:request_specific_fields].is_a?(Proc))
+        raise ArgumentError, "Invalid request_specific_fields' format: #{options[:request_specific_fields]}"
+      end
+    end
     unless mode == nil ||
            mode == 'r' || mode == 'rb' ||
            mode == File::RDONLY
@@ -215,9 +220,17 @@ module OpenURI
     max_redirects = options[:max_redirects] || Options.fetch(:max_redirects)
     buf = nil
     while true
+      request_specific_fields = {}
+      if options.has_key? :request_specific_fields
+        request_specific_fields = if options[:request_specific_fields].is_a?(Hash)
+                                    options[:request_specific_fields]
+                                  else options[:request_specific_fields].is_a?(Proc)
+                                    options[:request_specific_fields].call(uri)
+                                  end
+      end
       redirect = catch(:open_uri_redirect) {
         buf = Buffer.new
-        uri.buffer_open(buf, find_proxy.call(uri), options)
+        uri.buffer_open(buf, find_proxy.call(uri), options.merge(request_specific_fields))
         nil
       }
       if redirect
@@ -237,6 +250,10 @@ module OpenURI
           options = options.dup
           options.delete :http_basic_authentication
         end
+        if options.include?(:request_specific_fields) && options[:request_specific_fields].is_a?(Hash)
+          # Send request specific headers only for the initial request.
+          options.delete :request_specific_fields
+        end
         uri = redirect
         raise "HTTP redirection loop: #{uri}" if uri_set.include? uri.to_s
         uri_set[uri.to_s] = true