Change http.server.duration and http.client.duration units to seconds (open-telemetry#3390)

Author: trask

semantic_conventions/metrics/http.yaml

@@ -4,7 +4,7 @@ groups:
     metric_name: http.server.duration
     brief: "Measures the duration of inbound HTTP requests."
     instrument: histogram
-    unit: "ms"
+    unit: "s"
     extends: attributes.http.server
     attributes:
       # todo (lmolkova) build tools don't populate grandparent attributes
@@ -84,7 +84,7 @@ groups:
     metric_name: http.client.duration
     brief: "Measures the duration of outbound HTTP requests."
     instrument: histogram
-    unit: "ms"
+    unit: "s"
     extends: attributes.http.client
     attributes:
       - ref: http.method

specification/metrics/semantic_conventions/http-metrics.md

@@ -32,10 +32,14 @@ operations. By adding HTTP attributes to metric events it allows for finely tune
 
 This metric is required.
 
+This metric SHOULD be specified with
+[`ExplicitBucketBoundaries`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#instrument-advice)
+of `[ 0, 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10 ]`.
+
 <!-- semconv metric.http.server.duration(metric_table) -->
 | Name     | Instrument Type | Unit (UCUM) | Description    |
 | -------- | --------------- | ----------- | -------------- |
-| `http.server.duration` | Histogram | `ms` | Measures the duration of inbound HTTP requests. |
+| `http.server.duration` | Histogram | `s` | Measures the duration of inbound HTTP requests. |
 <!-- endsemconv -->
 
 <!-- semconv metric.http.server.duration(full) -->
@@ -213,10 +217,14 @@ SHOULD NOT be set if only IP address is available and capturing name would requi
 
 This metric is required.
 
+This metric SHOULD be specified with
+[`ExplicitBucketBoundaries`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#instrument-advice)
+of `[ 0, 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10 ]`.
+
 <!-- semconv metric.http.client.duration(metric_table) -->
 | Name     | Instrument Type | Unit (UCUM) | Description    |
 | -------- | --------------- | ----------- | -------------- |
-| `http.client.duration` | Histogram | `ms` | Measures the duration of outbound HTTP requests. |
+| `http.client.duration` | Histogram | `s` | Measures the duration of outbound HTTP requests. |
 <!-- endsemconv -->
 
 <!-- semconv metric.http.client.duration(full) -->