Replace expressions engine (#133)

internal/eval/functions/format_test.go

@@ -0,0 +1,14 @@
+package functions
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFormat(t *testing.T) {
+	s, err := Format("Hello {0}, you have {1} new messages", "Alice", 5)
+	assert.NoError(t, err)
+	fmt.Println(s) // Hello Alice, you have 5 new messages
+}