Secure execution of validity period system chaincode

[diegomasini]

The chaincode to update the validity period needs to be executed by an authorized party. In order to guarantee this, two extensions to the system need to be added:

• The identity of the caller should be available somehow for the chaincode to perform a check.
• The ability to determine if the chaincode is executed directly or as a part of a nested execution of chaincodes. This is not as important as the first item, but it will be nice to have the check.

There is no support to perform this verification right now, but the solution for the validity period chaincode should be general for any system chaincode.

Adding @binhn @adecaro @elli-androulaki @muralisrini @srderson and @raullaprida to provide feedback on this.

[christo4ferris]

@diegomasini is this being actively worked? If not, and it is a future feature, it really should be proposed as such using the feature proposal process that the maintainers are finalizing.