MRT message encoder for BGP updates

[digizeph]

Overview

This pull request adds MRT encoding for TableDumpMessage and Bgp4Mp types of messages.

We test it by parsing messages from remote site, encode to MRT bytes, and then parse the encoded bytes again for comparison. See the following test snippet for details:

    #[test]
    fn test_encode_large() {
        let url = "http://archive.routeviews.org/route-views.amsix/bgpdata/2023.05/UPDATES/updates.20230505.0330.bz2";
        let parser = BgpkitParser::new(url).unwrap();
        for record in parser.into_record_iter() {
            let bytes = record.encode();
            let parsed_record = parse_mrt_record(&mut Cursor::new(bytes)).unwrap();
            assert_eq!(record, parsed_record);
        }
    }

• encoding for TableDumpMessage
• encoding for Bgp4Mp
• BMP to MRT
• integration tests
• code examples and documentation

The implementation for TableDumpMessageV2 will require more work and will be implemented in the near future.

Example usages

MRT encoding can be very useful when users want to archive BGP messages into MRT instead of reading from MRT files. This enables applications to implement features like:

• BGP message archival
• BMP stream to MRT files
• Store filtered BGP messages into MRT files for storage (e.g. use in bgpkit-monocle)
• Split/copy/distribute input MRT file into output MRT files