Improve documentation of ComponentMetricRequest

In particular clarify the use of the `namespace` attribute and its
relationship with the channel name.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

src/frequenz/sdk/microgrid/_data_sourcing/_component_metric_request.py

@@ -13,19 +13,23 @@
 
 @dataclass
 class ComponentMetricRequest:
-    """A request object to start streaming a metric for a component."""
+    """A request to start streaming a metric for a component.
 
-    namespace: str
-    """The namespace that this request belongs to.
+    This request is used by the resampling and data sourcing actors to allow other
+    actors to subscribe to the data stream of a component's metric.
 
-    Metric requests with a shared namespace enable the reuse of channels within
-    that namespace.
+    The channel to use to receive the data stream is determined by the by the client
+    creating the request, but need to be unique in the channel's registry. For this
+    a `namespace` is used to make the channel name unique.
 
-    If for example, an actor making a multiple requests, uses the name of the
-    actor as the namespace, then requests from the actor will get reused when
-    possible.
+    The actor processing the request then will start streaming the data to the channel
+    with the name constructed from the request, as requested by the client. One could
+    also see the `namespace` as a *client ID*.
     """
 
+    namespace: str
+    """The namespace that this request belongs to. See the class docs for more info."""
+
     component_id: int
     """The ID of the requested component."""