Validate blocks arrived from PV to CV

[dmugtasimov]

DEPENDS ON:

• Support Celery #415
• Create POST /api/v1/blocks/ API end-point for CVs to accept new blocks from PV #110

TODO:

• Implement as celery task
• Pick pending block by uuid
• If block number is less or equal to current block number log a warning, delete it from pending blocks and exit
• If block number is greater than next block number log a warning, schedule the next run of the task in X seconds (configurable) and exit
• If block number is equal to next block number then validate it
• If the block is invalid then log a warning, delete it from pending blocks and exit
• Validate that block is signed by current PV (to be added to blockchain business logic)
• If the block is valid add it to confirmed blocks (create a stub function) and send block confirmation request to each known node on the network

[dmugtasimov]

@fonar @andbortnik unassign the other one whoever takes this task first

[dmugtasimov]

Looks like #461 is a part of this task