expose get proposal by party through rest api

[jeremyletang]

close #2037

[jeremyletang]

@DomVega could you take a look at this one

[vega-ci-bot]

system-tests failed.

=== Test summary ===
../../grpcTesting/governance/newAssetTests.py .                          [100%]
../../grpcTesting/governance/newMarketGovTests.py EEEEEEEEEEEEEEEEEEEEEx [ 47%]
EEEEEEEEEEEEEEEEEEEEEEEE                                                 [100%]
 ERROR at setup of testVoteNDecline 
 ERROR at setup of testFutureExpiredReject 
 ERROR at setup of testVoteYNProposalDraw 
 ERROR at setup of testVoteYYNProposalPass 
 ERROR at setup of testNewMarketRejectNoStake 
 ERROR at setup of testNewMarketValidProposal 
 ERROR at setup of testGetAllProposals 
 ERROR at setup of testGetAllOfTheProposals[6] 
 ERROR at setup of testGetNewMarketProposals[6] 
 ERROR at setup of testGetAllOfTheProposals[2] 
 ERROR at setup of testGetNewMarketProposals[2] 
 ERROR at setup of testGetAllOfTheProposals[5] 
 ERROR at setup of testGetNewMarketProposals[5] 
 ERROR at setup of testGetAllOfTheProposals[4] 
 ERROR at setup of testGetNewMarketProposals[4] 
 ERROR at setup of testGetAllOfTheProposals[3] 
 ERROR at setup of testGetNewMarketProposals[3] 
 ERROR at setup of testGetProposalsByParty 
 ERROR at setup of testGetRejectedProposalsByParty 
 ERROR at setup of testGetOpenProposalsByParty 
 ERROR at setup of testGetVotesByParty 
 ERROR at setup of testNewMarketOpenSingleTok 
 ERROR at setup of testVoteYSmallHolder 
 ERROR at setup of testVoteYMediumNSmallHolder 
 ERROR at setup of testVoteTopUpSmallDuringVote 
 ERROR at setup of testVoteYNNoFundsProposal 
 ERROR at setup of testNewMarketInvalidParty 
 ERROR at setup of testInvalidEnactTime 
 ERROR at setup of testVoteYOwnOpenProposal 
 ERROR at setup of testVoteYOpenProposal 
 ERROR at setup of testVoteNOpenProposal 
 ERROR at setup of testVoteNoStakeOpenProposal 
 ERROR at setup of testVoteNoStakeAddFunds 
 ERROR at setup of testVoteRejectProposal 
 ERROR at setup of testVotePassedProposal 
 ERROR at setup of testVoteBothYNOpen 
 ERROR at setup of testVoteTwiceYSameUser 
 ERROR at setup of testVoteInvalidProposalID 
 ERROR at setup of testVoteEnactedMarket 
 ERROR at setup of testVoteDeclinedMarket 
 ERROR at setup of testVoteYTaintedKey 
 ERROR at setup of testNewMarketClosedProposal 
 ERROR at setup of testSubmitEnactedGTCOrder 
 ERROR at setup of testSubmitUnEnactedMarketGTCOrder 
 ERROR at setup of testFiftyYesVoteProposal 
../../grpcTesting/governance/newMarketTradesTests.py ............        [100%]
../../grpcTesting/margins/marginsTests.py F.                             [100%]
 testMarginLevelStoppedFOK 
../../grpcTesting/markets/marketsTests.py ..............                 [100%]
../../grpcTesting/orders/amendOrdersTests.py ........................... [ 87%]
....                                                                     [100%]
../../grpcTesting/orders/cancelOrdersTests.py .......................    [100%]
../../grpcTesting/orders/generalOrdersTests.py .............             [100%]
../../grpcTesting/orders/limitOrdersTests.py ...........                 [100%]
../../grpcTesting/orders/marketOrdersTests.py ........                   [100%]
../../grpcTesting/orders/mixedOrdersTests.py .....................       [100%]
../../grpcTesting/orders/negativeOrdersTests.py ........................ [ 57%]
....x.........s...                                                       [100%]
../../grpcTesting/parallel/submitParallelOrdersTests.py ........         [100%]
../../grpcTesting/parties/partiesTests.py ..                             [100%]
../../grpcTesting/trading/positionsTests.py ..                           [100%]
../../grpcTesting/trading/tradesTests.py ......F.....                    [100%]
 testCloseOutTraderBuyOrders 
../../grpcTesting/wallet/walletTests.py ................................ [ 91%]
...                                                                      [100%]
../../rest/orders/negativeOrdersTests.py .                               [100%]

[nzbaen]

Tested the impementation on my localhost and the test collects the correct information now.

This is the response from the system.

{
  "data": [
    {
      "proposal": {
        "ID": "P0000032103-0000000001",
        "reference": "ETHVUSD/DEC20/DOM",
        "partyID": "ee2b865b5e2e9aa4c5a40e52a096d132ad86c3f77b41600beed0e8dc1152b1f4",
        "state": "STATE_REJECTED",
        "timestamp": "1596640731030564970",
        "terms": {
          "closingTimestamp": "1596940730",
          "enactmentTimestamp": "1596940730",
          "validationTimestamp": "0",
          "newMarket": {
            "changes": {
              "instrument": {
                "name": "December 2020 ETH vs VUSD future DOM",
                "code": "CRYPTO:ETHVUSD/DEC20",
                "baseName": "DOM",
                "quoteName": "VUSD",
                "future": {
                  "maturity": "2020-12-31T23:59:59Z",
                  "asset": "VUSD"
                }
              },
              "decimalPlaces": "0",
              "metadata": [
              ],
              "openingAuctionDuration": "0",
              "continuous": {
                "tickSize": "2592000000000000"
              }
            }
          }
        },
        "reason": "PROPOSAL_ERROR_INSUFFICIENT_TOKENS"
      },
      "yes": [
      ],
      "no": [
      ],
      "yesParty": {
      },
      "noParty": {
      }
    }
  ]
}