docs(dr): Add DR about empty assetSelector validator (#1774)

* docs(dr): Add DR about empty assetSelector validator

* review suggestions

docs/development/decision-records/2025-01-30-empty-asset-selector-validator/README.md

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+# Add Validator to Block Contract Definitions with Empty Asset Selector
+
+## Decision
+
+Tractusx-edc will provide a feature that allows blocking the creation or update of contract definitions to contain
+an empty asset selector. This feature will have the option to be switched on/off, being off the default state.
+
+## Rationale
+
+The `assetsSelector` property is a query (similar to a SQL SELECT statement) that returns a set of assets the
+contract definition applies to. When left empty, the default behavior of the connector is to apply the contract
+definition to all registered assets.
+
+Unwillingly, mostly due to lack of proper connector usage knowledge, users might expose datasets that shouldn't be
+exposed.
+
+As changing the default behavior of the `assetSelector` is not an option - it is as such by design - preventing
+such exposure can be achieved by applying the following approach.
+
+## Approach
+
+- Provide an extension that registers in the `JsonObjectValidatorRegistry` a new `JsonObjectValidator` for the
+  `https://w3id.org/edc/v0.0.1/ns/ContractDefinition` type. This validator should replace the one provided by default
+  by the contract definitions api.
+- The registration of the new `JsonObjectValidator` should be conditioned to setting the connector configuration
+  `tx.edc.validator.contractdefinitions.block-empty-assets-selector=true`
+- Implement the new `JsonObjectValidator` which should behave similarly to the existing
+  `ContractDefinitionValidator` except it should fail the validation in case the creation/update of a contract
+  definition introduces an empty `assetSelector` properties and the mentioned new toggle is enabled.
+
+