Merge remote-tracking branch 'origin/4.0.0a1-dev' into feature/2888_Align_core_software_with_registry

docs/source/how_to_guides/extensible_rewards.rst

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+.. only:: comment
+
+    © Crown-owned copyright 2025, Defence Science and Technology Laboratory UK
+
+.. _about:
+
+Extensible Rewards
+******************
+Extensible Rewards differ from the previous reward mechanism used in PrimAITE v3.x as new reward
+types can be added without requiring a change to the RewardFunction class in rewards.py (PrimAITE
+core repository).
+
+Changes to reward class structure.
+==================================
+
+Reward classes are inherited from AbstractReward (a sub-class of Pydantic's BaseModel).
+Within the reward class there is a ConfigSchema class responsible for ensuring the config file data
+is in the correct format. This also means there is little (if no) requirement for and `__init__`
+method. The `.from_config` method is no longer required as it's inherited from `AbstractReward`.
+Each class requires an identifier string which is used by the ConfigSchema class to verify that it
+hasn't previously been added to the registry.
+
+Inheriting from `BaseModel` removes the need for an `__init__` method but means that object
+attributes need to be passed by keyword.
+
+To add a new reward class follow the example below. Note that the type attribute in the
+`ConfigSchema` class should match the type used in the config file to define the reward.
+
+.. code-block:: Python
+
+class DatabaseFileIntegrity(AbstractReward, identifier="DATABASE_FILE_INTEGRITY"):
+    """Reward function component which rewards the agent for maintaining the integrity of a database file."""
+
+    config: "DatabaseFileIntegrity.ConfigSchema"
+    location_in_state: List[str] = [""]
+    reward: float = 0.0
+
+    class ConfigSchema(AbstractReward.ConfigSchema):
+        """ConfigSchema for DatabaseFileIntegrity."""
+
+        type: str = "DATABASE_FILE_INTEGRITY"
+        node_hostname: str
+        folder_name: str
+        file_name: str
+
+    def calculate(self, state: Dict, last_action_response: "AgentHistoryItem") -> float:
+        """Calculate the reward for the current state.
+        pass
+
+
+
+Changes to YAML file.
+=====================
+.. code:: YAML
+
+    There's no longer a need to provide a `dns_server` as an option in the simulation section
+    of the config file.