Stop using CGI.parse due to support Ruby 3.5

lib/fluent/plugin/in_monitor_agent.rb

@@ -15,7 +15,6 @@
 #
 
 require 'json'
-require 'cgi'
 
 require 'fluent/config/types'
 require 'fluent/plugin/input'
@@ -150,9 +149,7 @@ def build_object(opts)
       def build_option(req)
         qs = Hash.new { |_, _| [] }
         # parse ?=query string
-        if req.query_string
-          qs.merge!(CGI.parse(req.query_string))
-        end
+        qs.merge!(req.query || {})
 
         # if ?debug=1 is set, set :with_debug_info for get_monitor_info
         # and :pretty_json for render_json_error

lib/fluent/plugin_helper/http_server/request.rb

@@ -14,7 +14,7 @@
 #    limitations under the License.
 #
 
-require 'cgi'
+require 'uri'
 require 'async/http/protocol'
 require 'fluent/plugin_helper/http_server/methods'
 
@@ -35,7 +35,13 @@ def headers
         end
 
         def query
-          @query_string && CGI.parse(@query_string)
+          if @query_string
+            hash = Hash.new { |h, k| h[k] = [] }
+            # For compatibility with CGI.parse
+            URI.decode_www_form(@query_string).each_with_object(hash) do |(key, value), h|
+              h[key] << value
+            end
+          end
         end
 
         def body

test/plugin/test_in_monitor_agent.rb

@@ -5,6 +5,7 @@
 require 'fluent/config'
 require 'fluent/event_router'
 require 'fluent/supervisor'
+require 'fluent/version'
 require 'net/http'
 require 'json'
 require_relative '../test_plugin_classes'