Add `MatrixEvent.getKeyForwardingUser` (#5128)
* Update dependency @matrix-org/matrix-sdk-crypto-wasm to v17
* Remove references to `ShieldStateCode.SentInClear`
This was never used, and is no longer exported, by rust-sdk-crypto-wasm, so we
need to remove references to it.
* Add `MatrixEvent.getKeyForwardingUser`
Expose information about keys forwarded via MSC4286, via a new method on
`MatrixEvent`.
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Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
