chore: update proto definition to v1.4.0

opentelemetry-proto/src/proto/tonic/opentelemetry.proto.metrics.v1.rs

@@ -3,6 +3,24 @@
 /// storage, OR can be embedded by other protocols that transfer OTLP metrics
 /// data but do not implement the OTLP protocol.
 ///
+/// MetricsData
+/// └─── ResourceMetrics
+///    ├── Resource
+///    ├── SchemaURL
+///    └── ScopeMetrics
+///       ├── Scope
+///       ├── SchemaURL
+///       └── Metric
+///          ├── Name
+///          ├── Description
+///          ├── Unit
+///          └── data
+///             ├── Gauge
+///             ├── Sum
+///             ├── Histogram
+///             ├── ExponentialHistogram
+///             └── Summary
+///
 /// The main difference between this message and collector protocol is that
 /// in this message there will not be any "control" or "metadata" specific to
 /// OTLP protocol.
@@ -71,7 +89,6 @@ pub struct ScopeMetrics {
 ///
 ///    <https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/data-model.md>
 ///
-///
 /// The data model and relation between entities is shown in the
 /// diagram below. Here, "DataPoint" is the term used to refer to any
 /// one of the specific data point value types, and "points" is the term used
@@ -83,7 +100,7 @@ pub struct ScopeMetrics {
 /// - DataPoint contains timestamps, attributes, and one of the possible value type
 ///    fields.
 ///
-///      Metric
+///     Metric
 ///   +------------+
 ///   |name        |
 ///   |description |
@@ -277,6 +294,9 @@ pub struct ExponentialHistogram {
 /// data type. These data points cannot always be merged in a meaningful way.
 /// While they can be useful in some applications, histogram data points are
 /// recommended for new applications.
+/// Summary metrics do not have an aggregation temporality field. This is
+/// because the count and sum fields of a SummaryDataPoint are assumed to be
+/// cumulative values.
 #[cfg_attr(feature = "with-schemars", derive(schemars::JsonSchema))]
 #[cfg_attr(feature = "with-serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(feature = "with-serde", serde(rename_all = "camelCase"))]
@@ -587,7 +607,8 @@ pub mod exponential_histogram_data_point {
     }
 }
 /// SummaryDataPoint is a single data point in a timeseries that describes the
-/// time-varying values of a Summary metric.
+/// time-varying values of a Summary metric. The count and sum fields represent
+/// cumulative values.
 #[cfg_attr(feature = "with-schemars", derive(schemars::JsonSchema))]
 #[cfg_attr(feature = "with-serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(feature = "with-serde", serde(rename_all = "camelCase"))]