Request: Typed creation of MavConnection implementations

[peterkrull]

I find the current way of using strings to construct a MavConnection implementer through mavlink::connect(..) a bit awkward. It feels more like an application-level interface and not a library level interface, making it harder to build on top of the existing connection code or just use e.g. the serial implementation directly.

What I propose would include:

• Make types which encode the description/configuration of a connection
• Expose the individual MavConnection implementations for direct creation.

I imagine it could look something like this:

// in: mavlink-core/connection
pub trait Connectable<M: Message>
where Self: Sized
{
    fn connect(&self) -> io::Result<Box<dyn MavConnection<M> + Sync + Send>>;
}

// in: mavlink-core/connection/serial
pub struct SerialConfig {
    pub port: String,
    pub baud: usize,
}

impl<M: Message> Connectable<M> for SerialConfig {
    // impl
}

// in: mavlink-core/connection/tcp
pub struct TcpConfig {
    pub addr: SocketAddr,
    pub out: bool,
}

impl<M: Message> Connectable<M> for TcpConfig {
    // impl
}

// And so on..

which would make it fairly easy to implement a string-parser like:

match argument.split_whitespace().collect::<Vec<_>>().as_slice() {
    ["serial", port, baud] => SerialConfig {
        port: port.to_string(),
        baud: baud.parse().ok()?,
    }.connect()?,
    
    [conn @ "tcpin" | "tcpout", addr] => TcpConfig {
        addr: SocketAddr::from_str(port).ok()?,
        out: if conn == &"tcpout" { true } else { false },
    }.connect()?,

    // and so on..
    _ => None, // some error
}

What do you think?