Add CHANGELOG for SDAF 3.18.0.0 release with improvements and bug fixes (Azure#982)

* Add CHANGELOG for SDAF 3.18.0.0 release with improvements and bug fixes

* Update contributor recognition in CHANGELOG for SDAF 3.18.0.0 release

---------

Co-authored-by: Kimmo Forss <kimforss@microsoft.com>

Author: KimForss

CHANGELOG/v3.18.0.0/CHANGELOG.md

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+# Release PR: SDAF 3.18.0.0
+
+## Problem
+
+The SAP Deployment Automation Framework required several critical improvements across multiple dimensions:
+
+1. **DevOps Integration Gaps** - Limited support for GitHub Actions workflows and inconsistent Azure App Configuration handling across deployment pipelines
+2. **Platform Support** - Missing support for Ubuntu 25.04 and incomplete Oracle Grid infrastructure provisioning
+3. **Deployment Reliability** - Key vault reference inconsistencies in managed DevOps scenarios causing deployment failures
+4. **Configuration Management** - Fragmented approach to storing and retrieving deployment parameters across control plane and workload zones
+5. **Infrastructure Gaps** - Missing marketplace plan configurations for observer VMs and incomplete Azure App Configuration integration
+
+## Solution
+
+### DevOps & Automation
+- **GitHub Actions Integration**:
+  - New Python script (`New-SDAFGitHubActions.py`) for automated SDAF GitHub Actions setup with retry logic and improved error handling
+  - Docker container support for GitHub Actions with optimized Dockerfile and container build workflow
+  - Updated Terraform version to 1.14.0 across repository
+- **Azure App Configuration**: Implemented comprehensive Terraform modules for App Configuration resources across SAP landscape and library modules with private DNS zone management
+- **Pipeline Script Refactoring**: Enhanced v2 pipeline scripts with platform-agnostic functions, improved variable management, and ECC PGP key generation support
+
+### Infrastructure & Platform Support
+- **Ubuntu 25.04 Support**: Updated deployment scripts and Terraform configurations to handle Ubuntu 25.04 ("plucky"), including Azure CLI repository adjustments
+- **Oracle Grid Enhancements**: Added CRS data/admin directories with dynamic permissions, implemented logical sector size handling for disk configurations
+- **Observer VM Marketplace Plans**: Added dynamic plan configuration blocks to properly provision marketplace-based observer VMs
+
+### Deployment Reliability
+- **Key Vault Handling**: Refactored key vault ID retrieval to use control plane naming conventions consistently across all deployment scripts
+- **State Management**: Improved Terraform state migration handling with proper parameter sourcing and subscription ID management
+- **Variable Management**: Streamlined APPLICATION_CONFIGURATION_ID and APPLICATION_CONFIGURATION_NAME handling with proper fallbacks and validation
+
+### Configuration & Usability
+- **Distribution Variables**: Made distribution IDs available across all Ansible playbooks as group variables for improved consistency
+- **SUSE HA Optimization**: Set default vm.swappiness to 10 (down from 60) for SUSE HA clusters to improve performance
+- **Parameter Handling**: Refactored parameter passing to use dict with zip for improved code clarity
+- **Debug Improvements**: Enhanced error messages, logging, and conditional checks across deployment scripts
+
+### Bug Fixes
+- Fixed SAP_PARAMS handling in v1 Ansible script to properly handle file paths
+- Corrected conditional logic for App Configuration private DNS zones and virtual network links
+- Resolved empty Terraform state file handling in installer scripts
+- Fixed subscription ID extraction and environment variable exports
+
+## Tests
+
+### Prerequisites
+- Azure subscription with appropriate permissions
+- Ubuntu 25.04 test environment (if testing platform support)
+- GitHub repository with Actions enabled (for GitHub Actions testing)
+
+### Test Scenarios
+
+**1. GitHub Actions Setup**
+```bash
+cd deploy/scripts/py_scripts/SDAF-GitHub-Actions
+python New-SDAFGitHubActions.py
+# Verify: GitHub Actions workflows created, repository variables configured, Terraform version set to 1.14
+```
+
+**2. Ubuntu 25.04 Deployment**
+```bash
+# Deploy control plane on Ubuntu 25.04
+./deploy_control_plane_v2.sh --parameterfile <config_file>
+# Verify: Azure CLI repository correctly configured, Terraform 1.14.0 installed
+```
+
+**3. Azure App Configuration Integration**
+```bash
+# Deploy landscape with App Configuration
+terraform plan -var-file=<landscape_config>
+# Verify: App Configuration resources created, private DNS zones configured, key-value pairs populated
+```
+
+**4. Oracle Grid Setup**
+```bash
+# Deploy SAP system with Oracle database
+# Verify: CRS data/admin directories created with correct permissions, logical sector sizes applied
+```
+
+**5. Managed DevOps Scenario**
+```bash
+# Deploy using v2 pipeline scripts
+./deploy/scripts/pipeline_scripts/v2/01-webapp-configuration.sh
+# Verify: Key vault references resolved correctly, APPLICATION_CONFIGURATION_ID retrieved
+```
+
+**6. Observer VM with Marketplace Image**
+```bash
+# Deploy SAP system with observer VM using marketplace image
+# Verify: Plan block included in Terraform configuration, VM deploys successfully
+```
+
+## Notes
+
+### Breaking Changes
+- None identified - this release maintains backward compatibility with existing deployments
+
+### Migration Considerations
+- Existing deployments can upgrade in place
+- New Terraform 1.14.0 version requires validation of provider compatibility in custom modules
+- App Configuration integration is additive and does not affect existing deployments without App Configuration
+
+### Known Limitations
+- Docker container support for GitHub Actions is experimental and requires container registry access
+- Ubuntu 25.04 support is based on pre-release repositories which may change
+
+### Dependencies Updated
+This release includes multiple dependency version bumps:
+- actions/checkout: 5.0.0 → 5.0.1
+- actions/upload-artifact: 4.6.2 → 5.0.0 (major version bump)
+- github/codeql-action: 4.31.1 → 4.31.3
+- actions/dependency-review-action: 4.8.1 → 4.8.2
+- step-security/harden-runner: 2.13.1 → 2.13.2
+- Azure.ResourceManager.Compute: 1.12.0 → 1.13.0
+- System.Runtime.Caching: 9.0.10 → 10.0.0 (major version bump)
+- NuGet.Packaging: 6.14.0 → 7.0.0 (major version bump)
+- dotnet-ef: 9.0.6 → 10.0.0 (major version bump)
+
+### Contributor Recognition
+This release includes contributions from:
+- Kimmo Forss (@kimforss)
+- Nadeen Noaman (@nnoaman)
+- Copilot (code review and suggestions)
+- hdamecharla (@hdamecharla)
+