staking todos about moonbeam

[4meta5]

Right now, a nominator must call join_nominators for its first nomination and then nominate_new for every subsequent nomination. This is a bad interface -- move both into a nominate function that will choose which path to take based on whether there is an existing nomination associated with the caller.

[joelamouche]

need to use this polkadot-js type in order to make balance fields compact (like in frame/pallet-staking)

what do you mean by that? Mimic the polkadot-js types in the rust code?

[4meta5]

@joelamouche The Rust code change requires annotating the struct fields that use Balance type with #[compact]. The corresponding polkadot-js type needs to use bn.js or it isn't decoded correctly.

Let's not prioritize this until we're sure we want to optimize this implementation.

[4meta5]

Mostly addressed in #285 and will be tracked elsewhere from now on