[Server] Add Support for Sampling Groups to CustomNodeManager

[romanett]

Proposed changes

This PR introduces a MonitoredItemManager that manages MonitoredItems for the CustomNodeManager this IMonitoredItemManager abstraction has two default implementations, the MonitoredNodeMonitoredItemManager and the SamplingGroupMonitoredItemManager. These allow the CustomNodeManger to manage DataChangeMonitoredItems using the Sampling Group mechanism instead of using the MonitoredNode functionality.

This PR is a first step to allow to obsolete the CoreNodeManager having it´s own implementation of the INodeManager Interface, but instead relying on the proven mechanims of the CustomNodeManager.

This PR also allows to increase the test coverage of the SamplingGroup implementation, that is not covered by tests yet.

The CustomNodeManger has a new constructor overload, that allows to specify if the sampling group mechanism shall be used.

The Reference Server is extended with a new Property UseSamplingGroupsInReferenceNodeManager that allows to enable the use of Sampling Groups in the Reference Node Manager so CTT tests can be carried out with the Sampling Groups.

The Parameter is also enabled in the Reference Server Test to verify the implementation of the sampling group.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds functionality)
• Test enhancement (non-breaking change to increase test coverage)
• Breaking change (fix or feature that would cause existing functionality to not work as expected, requires version increase of Nuget packages)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc.
• I have signed the CLA.
• I ran tests locally with my changes, all passed.
• I fixed all failing tests in the CI pipelines.
• I fixed all introduced issues with CodeQL and LGTM.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added necessary documentation (if appropriate).
• Any dependent changes have been merged and published in downstream modules.

Further comments

[codecov]

Codecov Report

❌ Patch coverage is 68.72852% with 91 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.95%. Comparing base (6df0d13) to head (2899b34).
⚠️ Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
...MonitoredItem/SamplingGroupMonitoredItemManager.cs	47.87%	43 Missing and 6 partials ⚠️
...ies/Opc.Ua.Server/Diagnostics/CustomNodeManager.cs	73.00%	26 Missing and 1 partial ⚠️
...MonitoredItem/MonitoredNodeMonitoredItemManager.cs	88.04%	6 Missing and 5 partials ⚠️
....Server/NodeManager/MonitoredItem/SamplingGroup.cs	0.00%	0 Missing and 3 partials ⚠️
.../NodeManager/MonitoredItem/SamplingGroupManager.cs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3075      +/-   ##
==========================================
+ Coverage   57.44%   57.95%   +0.50%     
==========================================
  Files         357      358       +1     
  Lines       69245    69339      +94     
  Branches    14235    14266      +31     
==========================================
+ Hits        39780    40186     +406     
+ Misses      25194    24833     -361     
- Partials     4271     4320      +49     

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[Copilot]

Pull Request Overview

This PR introduces support for sampling groups to the CustomNodeManager by abstracting monitored item management into an IMonitoredItemManager interface with two implementations: one for sampling groups and one for the traditional monitored node mechanism. Key changes include adding new methods (e.g., SetMonitoringMode) to both server and client test services, updating the CustomNodeManager to use the new abstraction, and enabling sampling groups via the ReferenceServer and related configuration.

Reviewed Changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Tests/Opc.Ua.Server.Tests/ServerTestServices.cs	Added SetMonitoringMode method to forward calls to the underlying server, aligning with the new sampling group support.
Tests/Opc.Ua.Server.Tests/ServerFixture.cs	Added a sampling groups flag and integrated a call to enable sampling groups in the ReferenceServer during startup.
Tests/Opc.Ua.Server.Tests/ReferenceServerTest.cs	Updated tests to set UseSamplingGroupsInReferenceNodeManager and added a delay when sampling groups are active.
Tests/Opc.Ua.Client.Tests/ClientTestServices.cs	Added a SetMonitoringMode method in the client test services to complement server changes.
Libraries/Opc.Ua.Server/NodeManager/MonitoredItem/SamplingGroupMonitoredItemManager.cs	New implementation for managing monitored items when using sampling groups, including adjustments for zero sampling intervals.
Libraries/Opc.Ua.Server/Diagnostics/CustomNodeManager.cs	Refactored to delegate monitored item management to the new IMonitoredItemManager and updated event subscription and restoration code.
Applications/Quickstarts.Servers/ReferenceServer/*	Updated the ReferenceServer and related utilities to respect the sampling groups flag and pass it to the CustomNodeManager.

[romanett]

@marcschier The changes are nonbreaking

[mrsuciu]

Still some work to be done on the SamplingGroup since it might leak instances with the current logic.

[romanett]

@mrsuciu I fixed the disposal of Sampling groups, as soon as a subscription times out it deletes all MIs and this triggers a disposal of the sampling group.