The prototype for a logging filter. The filter callback will be
invoked for each request or response, and should analyze it and
return a #SoupLoggerLogLevel value indicating how much of the
message to log. Eg, it might choose between %SOUP_LOGGER_LOG_BODY
and %SOUP_LOGGER_LOG_HEADERS depending on the Content-Type.
The prototype for a logging filter. The filter callback will be invoked for each request or response, and should analyze it and return a #SoupLoggerLogLevel value indicating how much of the message to log. Eg, it might choose between %SOUP_LOGGER_LOG_BODY and %SOUP_LOGGER_LOG_HEADERS depending on the Content-Type.