feat(gl): add immutable postgres ledger storage

infrastructure/postgres/migration_test.go

@@ -0,0 +1,26 @@
+package postgres
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestInitialMigrationContainsLedgerSafetyGuards(t *testing.T) {
+	contents, err := migrationFiles.ReadFile("migrations/000001_init.up.sql")
+	if err != nil {
+		t.Fatal(err)
+	}
+	schema := string(contents)
+	for _, required := range []string{
+		"amount numeric(38, 18)",
+		"idempotency_key text NOT NULL UNIQUE",
+		"guard_journal_seal",
+		"journal is not balanced per asset",
+		"cannot append to a sealed journal",
+		"reject_ledger_mutation",
+	} {
+		if !strings.Contains(schema, required) {
+			t.Fatalf("migration is missing %q", required)
+		}
+	}
+}