Implement (non-) membership proof for an MPT element with a given key

[kushti]

For client applications (like light clients) this would be very helpful. There's an implementation of this functionality in Geth.

[lemastero]

Thank you @kushti for reporting 🙇
I am working on exposing getProof using JSON-RPC endpoint as described in EIP-1186. The next step will be exactly non-membership proof.

[drospa]

Hello @kushti,

we have a solution for both membership and non membership. They are both merged into development branch, they will be available in our next release.

#869
#899

[dzajkowski]

Looks done, closing. @kushti thanks for reporting!