x-pack/filebeat/input/cel: make http functions always available (#40912)

HTTP functions were previously conditional on the resource URL being an
HTTP/HTTPS URL. In hindsight, this offers no benefits and can result in
confusing errors when the end user enters an invalid URL for an HTTP-based
integration. Instead of a URL-related or HTTP-related error, the user is
given a compilation error indicating that the HTTP-related function that
are being called (and they may not be aware of in any way) are not valid
references. So let's just always make them available.

(cherry picked from commit 14337dd)

CHANGELOG.next.asciidoc

@@ -303,6 +303,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Allow attribute selection in the Active Directory entity analytics provider. {issue}40482[40482] {pull}40662[40662]
 - Improve error quality when CEL program does not correctly return an events array. {pull}40580[40580]
 - Add `use_kubeadm` config option for filebeat (both filbeat.input and autodiscovery) in order to toggle kubeadm-config api requests {pull}40301[40301]
+- Make HTTP library function inclusion non-conditional in CEL input. {pull}40912[40912]
 
 *Auditbeat*
 

x-pack/filebeat/input/cel/config.go

@@ -81,15 +81,11 @@ func (c config) Validate() error {
 		return fmt.Errorf("failed to check regular expressions: %w", err)
 	}
 	// TODO: Consider just building the program here to avoid this wasted work.
-	var client *http.Client
-	if wantClient(c) {
-		client = &http.Client{}
-	}
 	var patterns map[string]*regexp.Regexp
 	if len(c.Regexps) != 0 {
 		patterns = map[string]*regexp.Regexp{".": nil}
 	}
-	_, _, err = newProgram(context.Background(), c.Program, root, client, nil, nil, patterns, c.XSDs, logp.L().Named("input.cel"), nil)
+	_, _, err = newProgram(context.Background(), c.Program, root, &http.Client{}, nil, nil, patterns, c.XSDs, logp.L().Named("input.cel"), nil)
 	if err != nil {
 		return fmt.Errorf("failed to check program: %w", err)
 	}

x-pack/filebeat/input/cel/input.go

@@ -727,9 +727,6 @@ func getLimit(which string, rateLimit map[string]interface{}, log *logp.Logger)
 const lumberjackTimestamp = "[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]T[0-9][0-9]-[0-9][0-9]-[0-9][0-9].[0-9][0-9][0-9]"
 
 func newClient(ctx context.Context, cfg config, log *logp.Logger, reg *monitoring.Registry) (*http.Client, *httplog.LoggingRoundTripper, error) {
-	if !wantClient(cfg) {
-		return nil, nil, nil
-	}
 	c, err := cfg.Resource.Transport.Client(clientOptions(cfg.Resource.URL.URL, cfg.Resource.KeepAlive.settings())...)
 	if err != nil {
 		return nil, nil, err
@@ -1012,14 +1009,12 @@ func newProgram(ctx context.Context, src, root string, client *http.Client, limi
 		lib.Debug(debug(log, trace)),
 		lib.File(mimetypes),
 		lib.MIME(mimetypes),
+		lib.HTTPWithContext(ctx, client, limiter, auth),
 		lib.Limit(limitPolicies),
 		lib.Globals(map[string]interface{}{
 			"useragent": userAgent,
 		}),
 	}
-	if client != nil {
-		opts = append(opts, lib.HTTPWithContext(ctx, client, limiter, auth))
-	}
 	if len(patterns) != 0 {
 		opts = append(opts, lib.Regexp(patterns))
 	}