Invalid Packet Length Hotfix

[dmitri-mcguckin]

Closes Issue #53

This is a hotfix for the BeaconPacketPreprocessor class as it assumes that anything arriving in the UDP port is the correct length.

I simply added an extra config for packetSize onto the packet-preprocessor args and a length check for each ingesting packet, if it is not the exact length, then the packet will be rejected, logged as such, and a warn event will be produced in the Yamcs event streamer.

While investigating this issue, more problematic issues with implementation came up.

• EDL Packets are assumed to be created with the correct length
• HMAC Keys are still loaded from environment variables
• Many constructors call their parent constructors with child functions and with no error checking whatsoever

In addition to other missing features, such as storing sequence numbers in YDB.

So a subsequent deeper-clean of all the Packet Config system will be needed.