feat(proto): add governance proposal/vote RPC definitions

protobufs/operator/governance.proto

@@ -0,0 +1,66 @@
+syntax = "proto3";
+
+package arbiter.operator.governance;
+
+message Request {
+  oneof payload {
+    CreateProposalRequest create = 1;
+    CastVoteRequest       vote   = 2;
+    QueryPendingRequest   query  = 3;
+  }
+}
+
+message CreateProposalRequest {
+  oneof kind {
+    ApproveSdkClientPayload approve_sdk_client = 1;
+  }
+  optional uint32 ttl_secs = 2;
+}
+
+message ApproveSdkClientPayload {
+  int32 client_id = 1;
+}
+
+message CastVoteRequest {
+  int32 proposal_id = 1;
+  bool  approve     = 2;
+  bytes signature   = 3;
+}
+
+message QueryPendingRequest {}
+
+message Response {
+  oneof payload {
+    CreateProposalResponse created  = 1;
+    VoteResponse           voted    = 2;
+    QueryPendingResponse   pending  = 3;
+  }
+}
+
+message CreateProposalResponse {
+  int32 proposal_id = 1;
+}
+
+message VoteResponse {
+  VoteOutcome outcome = 1;
+}
+
+enum VoteOutcome {
+  VOTE_OUTCOME_UNSPECIFIED  = 0;
+  VOTE_OUTCOME_PENDING      = 1;
+  VOTE_OUTCOME_APPROVED     = 2;
+  VOTE_OUTCOME_REJECTED     = 3;
+}
+
+message ProposalSummary {
+  int32  id            = 1;
+  string kind          = 2;
+  int32  initiator_id  = 3;
+  int64  expires_at    = 4;
+  int64  approve_count = 5;
+  int64  reject_count  = 6;
+}
+
+message QueryPendingResponse {
+  repeated ProposalSummary proposals = 1;
+}