Server parameters currently have no mechanism to carry arbitrary metadata. Other subsystems (starting with PQS query knobs) need to annotate parameters with subsystem-specific data available at both build-time and runtime. Add a generic annotations: block to the IDL compiler that parses an opaque YAML subtree and exposes it as BSON via ServerParameter::annotations(). The compiler stores and serializes annotations without interpreting their content, the semantic meaning is left to downstream consumers.