Complete message validation

[simone-kalbermatter]

To address issue #1375, the MessageValidator class was implemented. The functions it contains are used to validate message data objects at their creation.

The goal is to eventually validate all messages. The MessageValidator can be extended to add more validation functions. Here is the main documentation you will need.

Message data objects that are already validated:

consensus

• [ ] AcceptValue
• [ ] ConsensusAccept
• [ ] ConsensusElect
• [ ] ConsensusElectAccept
• [ ] ConsensusFailure
• [ ] ConsensusKey
• [ ] ConsensusLearn
• [ ] ConsensusPrepare
• [ ] ConsensusPromise
• [ ] LearnValue
• [ ] PrepareValue
• [ ] PromiseValue
• [ ] ProposeValue

digitalcash

• [ ] Input
• [ ] Output
• [ ] PostTransactionCoin
• [ ] ScriptInput
• [ ] ScriptOutput
• [ ] Transaction

election - 100% done !

• [x] CastVote
• [x] ElectionEnd
• [x] ElectionKey
• [x] ElectionOpen
• [x] ElectionQuestion
• [x] ElectionResult
• [x] ElectionResultQuestion
• [x] ElectionSetup
• [x] EncryptedVote
• [x] PlainVote
• [x] QuestionResult

federation - 99% done

• [x] ChallengeRequest
• [x] Challenge (TODO: add a hex check on the challenge)
• [x] FederationExpect
• [x] FederationInit
• [x] FederationResult
• [x] TokensExchange

gossiping - 100% done !

• [X] Rumor

lao - 100% done !

• [x] CreateLao
• [x] GreetLao
• [x] StateLao
• [x] UpdateLao

meeting

• [x] CreateMeeting
• [x] StateMeeting

message

• [ ] WitnessMessageSignature

popcha

• [ ] PoPCHAAuthentication

rollcall - 100% done !

• [x] CloseRollCall
• [x] CreateRollCall
• [x] OpenRollCall

socialmedia - 33% done!

• [ ] AddChirp
• [x] AddReaction
• [ ] DeleteChirp
• [X] DeleteReaction
• [ ] NotifyAddChirp
• [ ] NotifyDeleteChirp