Migrate to libbuildpack-dynatrace (#1205)

Replace custom Dynatrace extension with official libbuildpack-dynatrace
library, following the same pattern as go-buildpack.

Changes:
- Add libbuildpack-dynatrace v1.8.0 dependency
- Implement Dynatrace hook in src/php/hooks/dynatrace.go
- Add hooks_debug.go for debugging support (BP_DEBUG)
- Remove custom dynatrace extension implementation
- Remove dynatrace extension registration from supply/finalize
- Update README to reflect new integration approach

The new implementation uses the standard libbuildpack hook system
during AfterCompile phase, ensuring Dynatrace software support and
compatibility with other Cloud Foundry buildpacks.

Fixes #1205

Author: ramonskie

README.md

@@ -90,10 +90,10 @@ The project is broken down into the following directories:
     - `supply/` - Dependency installation (PHP, HTTPD, Nginx)
     - `finalize/` - Final configuration and setup
     - `release/` - Release information
-    - `extensions/` - Extension system (composer, newrelic, dynatrace, appdynamics, sessions)
+    - `extensions/` - Extension system (composer, newrelic, appdynamics, sessions)
     - `config/` - Configuration management
     - `options/` - Options parsing
-    - `hooks/` - Lifecycle hooks
+    - `hooks/` - Lifecycle hooks (dynatrace integration)
     - `integration/` - Integration tests
     - `unit/` - Unit tests
   - `defaults/` - Default configuration files
@@ -145,7 +145,7 @@ The buildpack includes several built-in extensions written in Go:
 
 - **[composer](src/php/extensions/composer/)** - [Downloads, installs and runs Composer](http://docs.cloudfoundry.org/buildpacks/php/gsg-php-composer.html). Automatically detects PHP version requirements from `composer.json` and validates against locked dependencies.
 - **[newrelic](src/php/extensions/newrelic/)** - [Downloads, installs and configures the NewRelic agent for PHP](http://docs.cloudfoundry.org/buildpacks/php/gsg-php-newrelic.html)
-- **[dynatrace](src/php/extensions/dynatrace/)** - Downloads and configures Dynatrace OneAgent. Looks for a bound service with name `dynatrace` and credentials containing `apiurl`, `environmentid`, and `apitoken`.
+- **[dynatrace](src/php/hooks/dynatrace.go)** - Downloads and configures Dynatrace OneAgent using the official [libbuildpack-dynatrace](https://github.com/Dynatrace/libbuildpack-dynatrace) library. Looks for a bound service with name `dynatrace` and credentials containing `apiurl`, `environmentid`, and `apitoken`.
 - **[appdynamics](src/php/extensions/appdynamics/)** - Downloads and configures AppDynamics agent
 - **[sessions](src/php/extensions/sessions/)** - [Configures PHP to store session information in a bound Redis or Memcached service instance](http://docs.cloudfoundry.org/buildpacks/php/gsg-php-sessions.html)
 

go.mod

@@ -3,6 +3,7 @@ module github.com/cloudfoundry/php-buildpack
 go 1.24.0
 
 require (
+	github.com/Dynatrace/libbuildpack-dynatrace v1.8.0
 	github.com/cloudfoundry/libbuildpack v0.0.0-20251203175254-7be530ec9fef
 	github.com/cloudfoundry/switchblade v0.9.4
 	github.com/onsi/ginkgo/v2 v2.27.2

go.sum

@@ -622,6 +622,8 @@ github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym
 github.com/CycloneDX/cyclonedx-go v0.7.1/go.mod h1:N/nrdWQI2SIjaACyyDs/u7+ddCkyl/zkNs8xFsHF2Ps=
 github.com/DataDog/datadog-go v3.2.0+incompatible/go.mod h1:LButxg5PwREeZtORoXG3tL4fMGNddJ+vMq1mwgfaqoQ=
 github.com/DataDog/zstd v1.4.5/go.mod h1:1jcaCB/ufaK+sKp1NBhlGmpz41jOoPQ35bpF36t7BBo=
+github.com/Dynatrace/libbuildpack-dynatrace v1.8.0 h1:VNcd8+rurUUdY12emGfLGUUj5cMH4hkNgrdk8LO3dHE=
+github.com/Dynatrace/libbuildpack-dynatrace v1.8.0/go.mod h1:Uu9aa5UFAk1Ua+zZXnvzo+avDXuEi+GtegeOyja9xg4=
 github.com/GoogleCloudPlatform/docker-credential-gcr v2.0.5+incompatible/go.mod h1:BB1eHdMLYEFuFdBlRMb0N7YGVdM5s6Pt0njxgvfbGGs=
 github.com/JohnCGriffin/overflow v0.0.0-20211019200055-46fa312c352c/go.mod h1:X0CRv0ky0k6m906ixxpzmDRLvX58TFUKS2eePweuyxk=
 github.com/Masterminds/goutils v1.1.1/go.mod h1:8cTjp+g8YejhMuvIA5y2vz3BpJxksy863GQaJW2MFNU=