Merge #2906

2906: API additions for automating transaction building r=Jimbo4350 a=dcoutts

* Add API evaluateTransactionBalance

  Compute the total balance of the proposed transaction. Ultimately a
  valid transaction must be fully balanced: that is have a total value
  of zero.
    
  Finding the (non-zero) balance of partially constructed transaction
  is useful for adjusting a transaction to be fully balanced.

Co-authored-by: Duncan Coutts <duncan@well-typed.com>

cardano-api/cardano-api.cabal

@@ -94,6 +94,7 @@ library
   build-depends:        aeson             >= 1.5.6.0
                       , aeson-pretty      >= 0.8.5
                       , attoparsec
+                      , array
                       , base16-bytestring >= 1.0
                       , base58-bytestring
                       , bech32 >= 1.1.0
@@ -127,6 +128,7 @@ library
                       , ouroboros-network
                       , ouroboros-network-framework
                       , plutus-ledger-api
+                      , prettyprinter
                       , scientific
                       , shelley-spec-ledger
                       , small-steps

cardano-api/src/Cardano/Api.hs

@@ -221,6 +221,24 @@ module Cardano.Api (
     updateProposalSupportedInEra,
     scriptDataSupportedInEra,
 
+    -- ** Fee calculation
+    transactionFee,
+    estimateTransactionFee,
+    evaluateTransactionFee,
+    estimateTransactionKeyWitnessCount,
+
+    -- ** Script execution units
+    evaluateTransactionExecutionUnits,
+    ScriptExecutionError(..),
+    TransactionValidityIntervalError,
+
+    -- ** Transaction balance
+    evaluateTransactionBalance,
+
+    -- ** Building transactions with automated fees and balancing
+    makeTransactionBodyAutoBalance,
+    TxBodyErrorAutoBalance(..),
+
     -- * Signing transactions
     -- | Creating transaction witnesses one by one, or all in one go.
     Tx(Tx),
@@ -239,10 +257,6 @@ module Cardano.Api (
     makeShelleyKeyWitness,
     makeShelleyBootstrapWitness,
 
-    -- * Fee calculation
-    transactionFee,
-    estimateTransactionFee,
-
     -- * Transaction metadata
     -- | Embedding additional structured data within transactions.
     TxMetadata(..),