refactor: remove hardcoded versions from AppDynamics and NewRelic extensions

Replace hardcoded version strings and URLs with dynamic lookups from
manifest.yml using InstallOnlyVersion(). This ensures extension versions
are always pulled from the manifest, eliminating the need to update
code when bumping dependency versions.

Changes:
- Add InstallOnlyVersion() wrapper method to extensions.Installer
- Update AppDynamics extension to use InstallOnlyVersion()
- Update NewRelic extension to use InstallOnlyVersion()
- Remove hardcoded version 23.11.0-839 from AppDynamics
- Remove manual URL construction logic

This follows the same pattern used by PHP, HTTPD, and Nginx
installations in the buildpack.

Author: ramonskie

src/php/extensions/appdynamics/appdynamics.go

@@ -2,6 +2,7 @@ package appdynamics
 
 import (
 	"fmt"
+	"path/filepath"
 	"regexp"
 
 	"github.com/cloudfoundry/php-buildpack/src/php/extensions"
@@ -169,21 +170,10 @@ func (e *AppDynamicsExtension) Configure(ctx *extensions.Context) error {
 func (e *AppDynamicsExtension) Compile(ctx *extensions.Context, installer *extensions.Installer) error {
 	fmt.Println("Downloading AppDynamics package...")
 
-	// Merge defaults
-	if _, ok := ctx.Get("APPDYNAMICS_HOST"); !ok {
-		ctx.Set("APPDYNAMICS_HOST", "java-buildpack.cloudfoundry.org")
-	}
-	if _, ok := ctx.Get("APPDYNAMICS_VERSION"); !ok {
-		ctx.Set("APPDYNAMICS_VERSION", "23.11.0-839")
-	}
-	if _, ok := ctx.Get("APPDYNAMICS_PACKAGE"); !ok {
-		ctx.Set("APPDYNAMICS_PACKAGE", "appdynamics-{APPDYNAMICS_VERSION}.tar.bz2")
-	}
-	if _, ok := ctx.Get("APPDYNAMICS_DOWNLOAD_URL"); !ok {
-		ctx.Set("APPDYNAMICS_DOWNLOAD_URL", "https://{APPDYNAMICS_HOST}/appdynamics-php/{APPDYNAMICS_PACKAGE}")
-	}
+	buildDir := ctx.GetString("BUILD_DIR")
+	appdynamicsInstallDir := filepath.Join(buildDir, "appdynamics")
 
-	if err := installer.Package("APPDYNAMICS"); err != nil {
+	if err := installer.InstallOnlyVersion("appdynamics", appdynamicsInstallDir); err != nil {
 		return fmt.Errorf("failed to download AppDynamics package: %w", err)
 	}
 

src/php/extensions/extension.go

@@ -202,6 +202,14 @@ func (i *Installer) InstallDependency(dep libbuildpack.Dependency, outputDir str
 	return i.libbuildpackInst.InstallDependency(dep, outputDir)
 }
 
+// InstallOnlyVersion installs the only available version of a dependency
+func (i *Installer) InstallOnlyVersion(depName, installDir string) error {
+	if i.libbuildpackInst == nil {
+		return fmt.Errorf("libbuildpack installer not available")
+	}
+	return i.libbuildpackInst.InstallOnlyVersion(depName, installDir)
+}
+
 // Package downloads and installs a package based on a key in the context
 // This mimics Python's install.package('PACKAGENAME') method
 func (i *Installer) Package(packageKey string) error {

src/php/extensions/newrelic/newrelic.go

@@ -167,8 +167,8 @@ func (e *NewRelicExtension) Compile(ctx *extensions.Context, installer *extensio
 
 	fmt.Println("-----> Installing NewRelic")
 
-	// Install NewRelic package
-	if err := installer.Package("NEWRELIC"); err != nil {
+	newrelicInstallDir := filepath.Join(e.buildDir, "newrelic")
+	if err := installer.InstallOnlyVersion("newrelic", newrelicInstallDir); err != nil {
 		return fmt.Errorf("failed to install NewRelic package: %w", err)
 	}