Add randIntn function (#1475)

## Changes
<!-- Summary of your changes that are easy to understand -->
Add support for `math/rand.Intn` to DAB templates.

## Tests
<!-- How is this tested? -->
Unit tests.

libs/template/helpers.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math/rand"
 	"net/url"
 	"os"
 	"regexp"
@@ -46,6 +47,10 @@ func loadHelpers(ctx context.Context) template.FuncMap {
 		"regexp": func(expr string) (*regexp.Regexp, error) {
 			return regexp.Compile(expr)
 		},
+		// Alias for https://pkg.go.dev/math/rand#Intn. Returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n).
+		"random_int": func(n int) int {
+			return rand.Intn(n)
+		},
 		// A key value pair. This is used with the map function to generate maps
 		// to use inside a template
 		"pair": func(k string, v any) pair {

libs/template/helpers_test.go

@@ -3,6 +3,7 @@ package template
 import (
 	"context"
 	"os"
+	"strconv"
 	"strings"
 	"testing"
 
@@ -50,6 +51,24 @@ func TestTemplateRegexpCompileFunction(t *testing.T) {
 	assert.Contains(t, content, "1:fool")
 }
 
+func TestTemplateRandIntFunction(t *testing.T) {
+	ctx := context.Background()
+	tmpDir := t.TempDir()
+
+	ctx = root.SetWorkspaceClient(ctx, nil)
+	helpers := loadHelpers(ctx)
+	r, err := newRenderer(ctx, nil, helpers, "./testdata/random-int/template", "./testdata/random-int/library", tmpDir)
+	require.NoError(t, err)
+
+	err = r.walk()
+	assert.NoError(t, err)
+
+	assert.Len(t, r.files, 1)
+	randInt, err := strconv.Atoi(strings.TrimSpace(string(r.files[0].(*inMemoryFile).content)))
+	assert.Less(t, randInt, 10)
+	assert.Empty(t, err)
+}
+
 func TestTemplateUrlFunction(t *testing.T) {
 	ctx := context.Background()
 	tmpDir := t.TempDir()

libs/template/testdata/random-int/template/hello.tmpl

@@ -0,0 +1 @@
+{{print (random_int 10)}}