add PersistLoadWatermark

[npoltorapavlo]

RDK-42408 : Extend IWatermark to support Persistent Watermark Feature
this existed as a patch in RDK-V
bringing it to ThunderInterfaces

[Copilot]

Pull request overview

This PR extends the IWatermark interface to support persistent watermark features by adding a new method. The change originated as a patch in RDK-V and is being brought into ThunderInterfaces.

Changes:

• Added PersistLoadWatermark(uint32_t id) method to the IWatermark interface

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[Copilot]

The method name "PersistLoadWatermark" combines two distinct operations (persist and load) which violates the single responsibility principle. This creates ambiguity about what the method does. Consider splitting this into two separate methods: "PersistWatermark" for saving and "LoadWatermark" for loading, or clarify the intended behavior with a more descriptive name like "LoadPersistedWatermark" if it only loads a previously persisted watermark.

Suggested change

	virtual bool PersistLoadWatermark(uint32_t id) = 0;
	virtual bool LoadPersistedWatermark(uint32_t id) = 0;

[Copilot]

The method lacks documentation explaining its purpose, parameters, and return value semantics. Since this is an interface method being added to support persistent watermark features, it should include documentation that explains: what "persist and load" means in this context, what the 'id' parameter represents, and what the boolean return value indicates (success/failure conditions). This is especially important for interface methods that will be implemented by external parties.

Suggested change

	virtual bool UpdateWatermark(uint32_t id, uint32_t key, uint32_t size) = 0;
	virtual bool UpdateWatermark(uint32_t id, uint32_t key, uint32_t size) = 0;
	/**
	* Persist and/or load the state of the watermark identified by the given ID.
	*
	* Implementations typically use this method to store the current configuration
	* of a watermark to persistent storage and/or to restore a previously stored
	* configuration for the same watermark. The exact persist/load behavior may
	* depend on the concrete implementation.
	*
	* @param id
	* The unique identifier of the watermark whose state should be persisted
	* and/or loaded.
	*
	* @return
	* true if the persist/load operation completed successfully; false if the
	* operation failed (for example due to invalid ID, missing persisted data,
	* or storage errors).
	*/

[Copilot]

Adding a new method to an existing interface is a breaking change for the API. This change will break binary compatibility because any existing implementations of the IWatermark interface will not have this method implemented, causing vtable mismatches. Consider versioning the interface (e.g., IWatermark2) or using a COM versioning strategy to maintain backward compatibility with existing implementations.