Kernel: process inbox content
This only contain the first steps to achieving an E2E manual test:
* Loading an input
* Parsing the input
* Checking signatures if there's any (in our case for the moment, yes)
* Storing the hash + timestamp in the path
Balance checks are omitted as well as storing any index. These will be done in upcoming MRs.
Edited by Rodi-Can Bozman