admin: address CodeRabbit nitpicks (readonly review)

Four nitpick-tier findings collapsed into one commit:

- main.go: clarify the dynamoServer field doc — drop "exposed",
  which read like the field were exported. State explicitly that it
  is package-private state passed to startAdminFromFlags.

- internal/admin/dynamo_handler_test.go: drop the unused listOrder
  field on stubTablesSource (no test ever set it; carried over from
  an aborted "ordering bug" simulation). Replace the hand-rolled
  insertion sort with sort.Strings — stdlib idiom, less surface to
  maintain.

- adapter/dynamodb_admin_test.go: document why us-west-2 is a fine
  hardcoded region in the SigV4 client (the adapter does not enforce
  region match). Pointer for the future: if that ever changes, the
  region should be sourced from the same constant on both sides
  rather than re-hardcoded everywhere.

Author: bootjp

adapter/dynamodb_admin_test.go

@@ -172,6 +172,12 @@ func TestDynamoDB_AdminDescribeTable_GSI_SortedDeterministic(t *testing.T) {
 
 func newDynamoClient(t *testing.T, address string) *dynamodb.Client {
 	t.Helper()
+	// Region is intentionally arbitrary here. The test DynamoDB
+	// server does not enforce a region match in its SigV4 path —
+	// every existing adapter test uses "us-west-2" as a placeholder
+	// for the same reason. If the server later starts requiring a
+	// specific region, source it from the same constant the server
+	// reads instead of hardcoding it on each side independently.
 	cfg, err := config.LoadDefaultConfig(context.Background(),
 		config.WithRegion("us-west-2"),
 		config.WithCredentialsProvider(credentials.NewStaticCredentialsProvider("dummy", "dummy", "")),

internal/admin/dynamo_handler_test.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"net/http"
 	"net/http/httptest"
+	"sort"
 	"strings"
 	"testing"
 
@@ -14,30 +15,23 @@ import (
 )
 
 // stubTablesSource is the in-memory test double the dynamo handler
-// tests use. Returning sorted names from a map iteration mirrors the
-// adapter contract (lex-sorted by AdminListTables).
+// tests use. AdminListTables returns names in lex order, matching
+// the adapter's contract.
 type stubTablesSource struct {
-	tables    map[string]*DynamoTableSummary
-	listErr   error
-	descErr   error
-	listOrder []string // overrides sorted order if non-nil; lets us simulate adapter ordering bugs
+	tables  map[string]*DynamoTableSummary
+	listErr error
+	descErr error
 }
 
 func (s *stubTablesSource) AdminListTables(_ context.Context) ([]string, error) {
 	if s.listErr != nil {
 		return nil, s.listErr
 	}
-	if s.listOrder != nil {
-		out := make([]string, len(s.listOrder))
-		copy(out, s.listOrder)
-		return out, nil
-	}
 	out := make([]string, 0, len(s.tables))
 	for k := range s.tables {
 		out = append(out, k)
 	}
-	// AdminListTables's contract is sorted output.
-	stableSort(out)
+	sort.Strings(out)
 	return out, nil
 }
 
@@ -52,16 +46,6 @@ func (s *stubTablesSource) AdminDescribeTable(_ context.Context, name string) (*
 	return t, true, nil
 }
 
-// stableSort is a tiny helper to avoid importing sort in test files
-// that already have their own sort dependency style.
-func stableSort(s []string) {
-	for i := 1; i < len(s); i++ {
-		for j := i; j > 0 && s[j-1] > s[j]; j-- {
-			s[j-1], s[j] = s[j], s[j-1]
-		}
-	}
-}
-
 func newDynamoHandlerForTest(src TablesSource) *DynamoHandler {
 	return NewDynamoHandler(src)
 }

main.go

@@ -983,10 +983,12 @@ type runtimeServerRunner struct {
 	pprofToken      string
 	metricsRegistry *monitoring.Registry
 
-	// dynamoServer is populated by start() and exposed so the admin
-	// listener can call its SigV4-bypass admin entrypoints (see
-	// adapter/dynamodb_admin.go) without going through HTTP. It is
-	// nil until start() reaches the dynamo step.
+	// dynamoServer is populated by start() and made available to
+	// startAdminFromFlags in this package so the admin listener can
+	// call SigV4-bypass admin entrypoints (see
+	// adapter/dynamodb_admin.go) without going through HTTP. The
+	// field is unexported on purpose — it is package-private state,
+	// not a public API. Nil until start() reaches the dynamo step.
 	dynamoServer *adapter.DynamoDBServer
 }