Transaction retrry

[liningpan]

The async_bb8_diesel crate developed by Oxide supports transaction retry, which is necessary
when working with serializable transactions (especially cockroach db).

https://docs.rs/async-bb8-diesel/latest/async_bb8_diesel/trait.AsyncConnection.html

Would it possible to have something similar in diesel_async?

[weiznich]

I'm happy to accept a PR for this as long as it contains documentation + and a reasonable set of tests. Otherwise this is nothing I plan to work on in the next weeks/months for capacity reasons.