refactor(remote_config): move capability registration to feature modules

Move remote config capability and handler registration from central location
to feature-specific modules for better separation of concerns.

Changes:
- Create tracing/remote_config.js for APM_TRACING_* capabilities and handler
- Create openfeature/remote_config.js for FFE_FLAG_CONFIGURATION_RULES capability
- Remove remote_config/index.js wrapper, instantiate RemoteConfig directly in proxy
- Rename RemoteConfigManager class to RemoteConfig
- Rename remote_config/manager.js to remote_config/index.js
- Replace chai with node:assert/strict in remote_config tests
- Use real implementations in proxy tests instead of stubbing

This creates a consistent pattern where features own their remote config setup:
- Core APM tracing → tracing/remote_config.js (always enabled)
- OpenFeature → openfeature/remote_config.js (conditional)
- AppSec → appsec/remote_config.js (conditional)

Author: watson

packages/dd-trace/src/appsec/remote_config.js

@@ -11,8 +11,8 @@ let rc
 
 /**
  * Configures remote config handlers for appsec features
- * @param {Object} rcInstance - RemoteConfigManager instance
  *
+ * @param {Object} rcInstance - RemoteConfig instance
  * @param {Object} config - Tracer config
  * @param {Object} appsec - Appsec module
  */

packages/dd-trace/src/config/remote_config.js

@@ -0,0 +1,34 @@
+'use strict'
+
+const RemoteConfigCapabilities = require('../remote_config/capabilities')
+
+/**
+ * Configures remote config for core APM tracing functionality
+ *
+ * @param {Object} rc - RemoteConfig instance
+ * @param {Object} config - Tracer config
+ * @param {Function} enableOrDisableTracing - Function to enable/disable tracing based on config
+ */
+function enable (rc, config, enableOrDisableTracing) {
+  // Register core APM tracing capabilities
+  rc.updateCapabilities(RemoteConfigCapabilities.APM_TRACING_CUSTOM_TAGS, true)
+  rc.updateCapabilities(RemoteConfigCapabilities.APM_TRACING_HTTP_HEADER_TAGS, true)
+  rc.updateCapabilities(RemoteConfigCapabilities.APM_TRACING_LOGS_INJECTION, true)
+  rc.updateCapabilities(RemoteConfigCapabilities.APM_TRACING_SAMPLE_RATE, true)
+  rc.updateCapabilities(RemoteConfigCapabilities.APM_TRACING_ENABLED, true)
+  rc.updateCapabilities(RemoteConfigCapabilities.APM_TRACING_SAMPLE_RULES, true)
+
+  // APM_TRACING product handler - manages tracer configuration
+  rc.setProductHandler('APM_TRACING', (action, conf) => {
+    if (action === 'unapply') {
+      config.configure({}, true)
+    } else {
+      config.configure(conf.lib_config, true)
+    }
+    enableOrDisableTracing(config)
+  })
+}
+
+module.exports = {
+  enable
+}

packages/dd-trace/src/openfeature/remote_config.js

@@ -0,0 +1,31 @@
+'use strict'
+
+const RemoteConfigCapabilities = require('../remote_config/capabilities')
+
+/**
+ * Configures remote config handlers for openfeature feature flagging
+ *
+ * @param {Object} rc - RemoteConfig instance
+ * @param {Object} config - Tracer config
+ * @param {Function} getOpenfeatureProxy - Function that returns the OpenFeature proxy from tracer
+ */
+function enable (rc, config, getOpenfeatureProxy) {
+  // Always enable capability for feature flag configuration
+  // This indicates the library supports this capability via remote config
+  rc.updateCapabilities(RemoteConfigCapabilities.FFE_FLAG_CONFIGURATION_RULES, true)
+
+  // Only register product handler if the experimental feature is enabled
+  if (!config.experimental.flaggingProvider.enabled) return
+
+  // Set product handler for FFE_FLAGS
+  rc.setProductHandler('FFE_FLAGS', (action, conf) => {
+    // Feed UFC config directly to OpenFeature provider
+    if (action === 'apply' || action === 'modify') {
+      getOpenfeatureProxy()._setConfiguration(conf)
+    }
+  })
+}
+
+module.exports = {
+  enable
+}

packages/dd-trace/src/proxy.js

@@ -126,16 +126,11 @@ class Tracer extends NoopProxy {
       }
 
       if (config.remoteConfig.enabled && !config.isCiVisibility) {
-        const rc = require('./remote_config').enable(config)
+        const RemoteConfig = require('./remote_config')
+        const rc = new RemoteConfig(config)
 
-        rc.setProductHandler('APM_TRACING', (action, conf) => {
-          if (action === 'unapply') {
-            config.configure({}, true)
-          } else {
-            config.configure(conf.lib_config, true)
-          }
-          this._enableOrDisableTracing(config)
-        })
+        const tracingRemoteConfig = require('./config/remote_config')
+        tracingRemoteConfig.enable(rc, config, this._enableOrDisableTracing.bind(this))
 
         rc.setProductHandler('AGENT_CONFIG', (action, conf) => {
           if (!conf?.name?.startsWith('flare-log-level.')) return
@@ -165,14 +160,8 @@ class Tracer extends NoopProxy {
           DynamicInstrumentation.start(config, rc)
         }
 
-        if (config.experimental.flaggingProvider.enabled) {
-          rc.setProductHandler('FFE_FLAGS', (action, conf) => {
-            // Feed UFC config directly to OpenFeature provider
-            if (action === 'apply' || action === 'modify') {
-              this.openfeature._setConfiguration(conf)
-            }
-          })
-        }
+        const openfeatureRemoteConfig = require('./openfeature/remote_config')
+        openfeatureRemoteConfig.enable(rc, config, () => this.openfeature)
       }
 
       if (config.profiling.enabled === 'true') {