added custom_size_based_buffer class

Added the feature for size and time based flushing of buffer.
Added config options for max_interval and max_size. Once either one is
reached the events stored in the buffer will be flushed.

Updated kusto.rb

lib/logstash/outputs/kusto.rb

@@ -96,10 +96,6 @@ class LogStash::Outputs::Kusto < LogStash::Outputs::Base
   # Mapping name - deprecated, use json_mapping
   config :mapping, validate: :string, deprecated: true
 
-  config :max_size, validate => :number, default => 1000
-
-  config :max_interval, validate => :number, default => 60
-
   # Determines if local files used for temporary storage will be deleted
   # after upload is successful
   config :delete_temp_files, validate: :boolean, default: true
@@ -123,6 +119,12 @@ class LogStash::Outputs::Kusto < LogStash::Outputs::Base
   # Check Proxy URL can be over http or https. Dowe need it this way or ignore this & remove this
   config :proxy_protocol, validate: :string, required: false , default: 'http'
 
+  # Maximum size (number of events) of the buffer before it gets flushed, defaults to 1000
+  config :max_size, validate: :number, default: 1000
+
+  # Maximum interval (in seconds) before the buffer gets flushed, defaults to 60
+  config :max_interval, validate: :number, default: 60
+
   default :codec, 'json_lines'
 
   def register