store starting time of the proposal in its datum

... hardcoded to 0 upon creation for now

agora-sample/Sample/Governor.hs

@@ -80,6 +80,7 @@ import Sample.Shared (
   stake,
   stakeAddress,
   stakeAssetClass,
+  tmpProposalStartingTime,
  )
 import Test.Util (datumPair, toDatumHash)
 
@@ -236,6 +237,7 @@ createProposal =
                 , thresholds = defaultProposalThresholds
                 , votes = emptyVotesFor effects
                 , timingConfig = proposalTimingConfig
+                , startingTime = tmpProposalStartingTime
                 }
           )
       proposalOutput :: TxOut
@@ -411,6 +413,7 @@ mintGATs =
           , thresholds = defaultProposalThresholds
           , votes = proposalVotes
           , timingConfig = proposalTimingConfig
+          , startingTime = tmpProposalStartingTime
           }
       proposalInputDatum :: Datum
       proposalInputDatum = Datum $ toBuiltinData proposalInputDatum'

agora-sample/Sample/Proposal.hs

@@ -75,6 +75,7 @@ proposalCreation =
                 , thresholds = defaultProposalThresholds
                 , votes = emptyVotesFor effects
                 , timingConfig = proposalTimingConfig
+                , startingTime = tmpProposalStartingTime
                 }
           )
 
@@ -169,6 +170,7 @@ cosignProposal newSigners =
           , thresholds = defaultProposalThresholds
           , votes = emptyVotesFor effects
           , timingConfig = proposalTimingConfig
+          , startingTime = tmpProposalStartingTime
           }
       stakeDatum :: StakeDatum
       stakeDatum = StakeDatum (Tagged 50_000_000) signer2 []

agora-sample/Sample/Shared.hs

@@ -37,6 +37,7 @@ module Sample.Shared (
   proposalValidatorHash,
   proposalValidatorAddress,
   proposalTimingConfig,
+  tmpProposalStartingTime,
 
   -- ** Authority
   authorityToken,
@@ -76,6 +77,7 @@ import Agora.Proposal (
   ProposalThresholds (..),
  )
 import Agora.Proposal.Time (
+  ProposalStartingTime (..),
   ProposalTimingConfig (..),
  )
 import Agora.Stake (Stake (..))
@@ -197,6 +199,10 @@ proposalTimingConfig =
     , executingTime = 3000
     }
 
+-- FIXME: should be removed.
+tmpProposalStartingTime :: ProposalStartingTime
+tmpProposalStartingTime = ProposalStartingTime 0
+
 ------------------------------------------------------------------
 
 treasuryOut :: TxOut