Detect if a received message has been tampered with

[kbaley]

This issue was transferred from a private repository

NServiceBus has no built-in way to ensure that the received message is coming from a legitimate source and/or has not being tampered along the way while in flight.

At a sender, it should be possible to:

• configure endpoints to sign all outgoing messages
• sign specific messages using SendOptions
• configure signing options and algorithms

At the receiver:

• configure endpoints to validate an incoming message signature, if present
• configure endpoints to enforce the presence of a message signature and/or allow non signed messages
• configure signing options and algorithms

Right now, this can be done with a behavior but perhaps we can offer this as a supported package using an existing standard (e.g. JWT).

NOTE: This doesn't have to be (and probably shouldn't be) done in NServiceBus Core. It would likely work better as a separate package.