Map Serialize Error doesn't support serde(flatten)/serde_as(as = "vec(_,_)>")]

[pvichivanives]

Hi! I was wondering if the error: CSV serialize error: serializing maps is not supported, if you have a use case, please file an issue at https://github.com/BurntSushi/rust-csv could support using something like #[serde_as(as = "Vec<(_, _)>")] or #[serde(flatten)]

Since these would mean we wouldn't need to serialize the Map itself but use Serde's implementation of converting to the Vec/flatten it out first.