poll_transmit is large

[gretchenfrage]

Connection.poll_transmit is 582 lines. I think it should be split up somehow.

Maybe a good place to start would be to factor out the body of the loop over spaces? It accounts for 380 lines, and factoring it out would reduce rightward drift.

[djc]

This drifted by on HN recently, and I've definitely noticed this:

https://www.16elt.com/2024/09/25/first-book-of-byte-sized-tech/#Idea-2-Smaller-components-are-not-necessarily-better-for-modularity

I've long had a guideline that single-call functions are little suspect, so not sure this is the right direction (but, I haven't looked at your draft PR yet).

[gretchenfrage]

The "DatagramBuilder" idea Ralith noted in #2122 seems worth exploring