chore: adjusted to include common headers

While these are not currently used they could be and having them here will make future adjustments simpler by not having to look for them!

lib/json_rails_logger/constants.rb

@@ -2,4 +2,34 @@
 
 module JsonRailsLogger
   REQUEST_ID = :request_id
+  # * THE FOLLOWING ARE NOT CURRENTLY USED BUT AVAILABLE FOR FUTURE USE * #
+  # REQUEST_URI = :request_uri
+  # REQUEST_METHOD = :request_method
+  # REQUEST_PATH = :request_path
+  # SERVER_NAME = :server_name
+  # STATUS = :status
+  # DURATION = :duration
+  # USER_AGENT = :user_agent
+  # ACCEPT = :accept
+  # MESSAGE = :message
+  # EXCEPTION = :exception
+  # BACKTRACE = :backtrace
+  # CONTROLLER = :controller
+  # ACTION = :action
+  # PARAMS = :params
+  # IP = :ip
+  # AUTH = :auth
+  # HTTP_HOST = :http_host
+  # HTTP_VERSION = :http_version
+  # HTTP_REFERER = :http_referer
+  # HTTP_COOKIE = :http_cookie
+  # HTTP_ACCEPT_ENCODING = :http_accept_encoding
+  # HTTP_ACCEPT_LANGUAGE = :http_accept_language
+  # HTTP_ACCEPT_CHARSET = :http_accept_charset
+  # HTTP_CACHE_CONTROL = :http_cache_control
+  # HTTP_CONNECTION = :http_connection
+  # HTTP_UPGRADE_INSECURE_REQUESTS = :http_upgrade_insecure_requests
+  # HTTP_ORIGIN = :http_origin
+  # HTTP_DNT = :http_dnt
+  # HTTP_X_REQUEST_ID = :http_x_request_id
 end