Provide trait for Matrix API objects with ed25519 signatures
Currently stuff is kind of a mess in this regard. As there are a lot of functions with similar functionality for comfortably working with these objects, it would be good to have a trait for these data types for improved consistency.
Functionality to consider:
- verify own signature (potentially makes the two below redundant?)
- extract signature
- extract self without signature
(Probably incomplete) List of signed Matrix API objects
- device keys