docs: metadata conceptual doc

Signed-off-by: Todd Baert <todd.baert@dynatrace.com>

Author: toddbaert

docs/concepts/feature-flagging.md

@@ -22,3 +22,4 @@ Below is a non-exhaustive table of common feature flag use-cases, and how flagd
 | dynamic (context-sensitive) evaluation    | flagd evaluations are context sensitive. Rules can use arbitrary context attributes as inputs for flag evaluation logic.                                                                                                                                                         |
 | fractional evaluation / random assignment | flagd's [fractional](../reference/custom-operations/fractional-operation.md) custom operation supports pseudorandom assignment of flag values.                                                                                                                                   |
 | progressive roll-outs                     | Progressive roll-outs of new features can be accomplished by leveraging the [fractional](../reference/custom-operations/fractional-operation.md) custom operation as well as automation in your build pipeline, SCM, or infrastructure which updates the distribution over time. |
+| feature flag telemetry                    | flagd supports the OpenTelemetry conventions for feature flags, by returning compliant [resolution details](https://openfeature.dev/specification/types#resolution-details) and [metadata](../reference/monitoring.md#metadata), in addition to flag values.                     |

docs/reference/monitoring.md

@@ -161,3 +161,10 @@ scrape_configs:
 
 Once, configuration files are ready, use `docker-compose up` to start the local setup. With successful startup, you can
 access metrics through [Prometheus](http://localhost:9090/graph) & traces through [Jaeger](http://localhost:16686/).
+
+## Metadata
+
+[Flag metadata](https://openfeature.dev/specification/types/#flag-metadata) comprises auxiliary data pertaining to feature flags; it's highly valuable in telemetry signals.
+Flag metadata might consist of attributes indicating the version of the flag, an identifier for the flag set, ownership information about the flag, or other documentary information.
+flagd supports flag metadata in all its [gRPC protocols](../reference/specifications//protos.md), in [OFREP](../reference/flagd-ofrep.md), and in its [flag definitions](./flag-definitions.md#metadata).
+These attributes are returned with flag evaluations, and can be added to telemetry signals as outlined in the [OpenFeature specification](https://openfeature.dev/specification/appendix-d).