Part of https://github.com/vector-im/element-web/issues/21972. Eventually I want to replace the whole of the current `Crypto` implementation with an alternative implementation, but in order to get from here to there, I'm factoring out a common interface which will be implemented by both implementations.
I'm also determined to fix the problem where the innards of the crypto implementation are exposed to applications via the `MatrixClient.crypto` property.
It's not (yet) entirely clear what shape this interface should be, so I'm going with a minimal approach and adding things as we know we need them. This means that we need to keep the old `client.crypto` property around as well as a new `client.cryptoBackend` property. Eventually `client.crypto` will go away, but that will be a breaking change in the js-sdk.
Richard van der Hoff
9c17eb6c14