Implement proposal submission command

[jeremyletang]

This introduce a ProposalSubmission command instead of using the Proposal type in the command. This is a first step to separate properly our Command to submit a new proposal, and our proposal model.

Here's the difference between both data structures:

message ProposalSubmission {
  string reference = 1;
  ProposalTerms terms = 2 [(validator.field) = {msg_exists: true}];
}

message Proposal {
  enum State {
    // all enum state fields
  }

  string id = 1;
  string reference = 2;
  string party_id = 3 [(validator.field) = {string_not_empty : true}];
  State state = 4 [(validator.field) = {is_in_enum: true}];
  int64 timestamp = 5;
  ProposalTerms terms = 6 [(validator.field) = {msg_exists: true}];
  ProposalError reason = 7;
}

[ashleyvega]

LGTM

[ashleyvega]

Let's get this merged before v0.36.0, so all the API changes (votes, events, proposals) happen at once.

[jeremyletang]

Let's get this merged before v0.36.0, so all the API changes (votes, events, proposals) happen at once.

That’s my intent to get all these done as soon as possible