Raw Markdown displayed in command line help

[palant]

Describe the bug

Running a Pingora server with --help command line flag will produce descriptions including raw Markdown. Also, the names of command line flags unnecessarily. These are meant for online documentation and often make little sense as a command line help.

Pingora info

Please include the following information about your environment:

Pingora version: 2501d4a
Rust version: 1.79.0-nightly (28e7b2bc0 2024-04-05)
Operating system version: Fedora 39

Steps to reproduce

Run cargo run --example gateway -- --help from the command line.

Expected results

A human-readable output without any duplicated information.

Observed results

Raw Markdown and duplicated information on command line flags, pointless references to code (the command description in particular is meaningless) and references to code (ServerConf) that should have really been URLs:

basic 0.1.0
Command-line options

Call `Opt::from_args()` to build this object from the process's command line arguments.

USAGE:
    gateway [FLAGS] [OPTIONS]

FLAGS:
    -d, --daemon       
            Whether should run this server in the background
            
            `-d` or `--daemon` can be used
    -h, --help         
            Prints help information

        --nocapture    
            Not actually used. This flag is there so that the server is not upset seeing this flag passed from `cargo
            test` sometimes
    -t, --test         
            Test the configuration and exit
            
            When this flag is set, calling `server.bootstrap()` will exit the process without errors
            
            This flag is useful for upgrading service where the user wants to make sure the new service can start before
            shutting down the old server process.
            
            `-t` or `--test` can be used
    -u, --upgrade      
            Whether this server should try to upgrade from a running old server
            
            `-u` or `--upgrade` can be used
    -V, --version      
            Prints version information


OPTIONS:
    -c, --conf <conf>    
            The path to the configuration file.
            
            See [`ServerConf`] for more details of the configuration file.
            
            `-c` or `--conf` can be used

Additional context

The docstrings that this info is compiled from should really be adjusted. While an application extending the default command line options will overwrite the application description, adjusting the description of individual options is non-trivial.

Alternatively, the docstrings can be left unchanged and structopt help messages can be specified separately.