Alternative: Register mapper function of options instead of just the extra options

The solution described in comment https://github.com/coinbase/rosetta-sdk-go/pull/423#discussion_r914876672. It mostly demonstrates that it adds too much complexity for what it gains.

Author: bisgardo

go.mod

@@ -21,4 +21,4 @@ require (
 	github.com/btcsuite/btcd/btcutil v1.1.1
 )
 
-replace github.com/coinbase/rosetta-sdk-go => github.com/Concordium/rosetta-sdk-go v0.7.11-0.20220706095914-7942ab456d4f
+replace github.com/coinbase/rosetta-sdk-go => ../rosetta-sdk-go

pkg/tester/data.go

@@ -329,10 +329,14 @@ func InitializeData(
 		statefulsyncer.WithMaxConcurrency(config.MaxSyncConcurrency),
 		statefulsyncer.WithPastBlockLimit(config.MaxReorgDepth),
 		statefulsyncer.WithSeenConcurrency(int64(config.SeenBlockWorkers)),
-		statefulsyncer.WithExtraSyncerOpts(
-			syncer.WithCustomHelper(func(h syncer.Helper) syncer.Helper {
-				return newConcordiumHelper(h)
-			}),
+		statefulsyncer.WithCustomSyncerOpts(
+			func(opts ...syncer.Option) []syncer.Option {
+				return append(
+					opts,
+					syncer.WithCustomHelper(func(h syncer.Helper) syncer.Helper {
+						return newConcordiumHelper(h)
+					}))
+			},
 		),
 	}
 	if config.Data.PruningFrequency != nil {