add protected constructors for metric instrumentation in Temporalio.Common namespace (#431)

Author: robcao

README.md

@@ -1115,6 +1115,7 @@ activity context:
 * `Heartbeater` - Callback invoked each heartbeat.
 * `WorkerShutdownTokenSource` - Token source for issuing worker shutdown.
 * `PayloadConverter` - Defaulted to default payload converter.
+* `MetricMeter` - Defaulted to noop meter.
 
 ### OpenTelemetry Tracing Support
 

src/Temporalio/Common/MetricCounter.cs

@@ -18,6 +18,17 @@ internal MetricCounter(MetricDetails details)
         {
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MetricCounter{T}" /> class.
+        /// </summary>
+        /// <param name="name">The name of the counter.</param>
+        /// <param name="unit">The optional unit of measurement for the values recorded by the counter.</param>
+        /// <param name="description">The optional description of the counter.</param>
+        protected MetricCounter(string name, string? unit = null, string? description = null)
+            : this(new(name, unit, description))
+        {
+        }
+
         /// <summary>
         /// Add the given value to the counter.
         /// </summary>

src/Temporalio/Common/MetricGauge.cs

@@ -18,6 +18,17 @@ internal MetricGauge(MetricDetails details)
         {
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MetricGauge{T}" /> class.
+        /// </summary>
+        /// <param name="name">The name of the gauge.</param>
+        /// <param name="unit">The optional unit of measurement for the values recorded by the gauge.</param>
+        /// <param name="description">The optional description of the gauge.</param>
+        protected MetricGauge(string name, string? unit = null, string? description = null)
+            : this(new(name, unit, description))
+        {
+        }
+
         /// <summary>
         /// Set the given value on the gauge.
         /// </summary>

src/Temporalio/Common/MetricHistogram.cs

@@ -18,6 +18,17 @@ internal MetricHistogram(MetricDetails details)
         {
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MetricHistogram{T}" /> class.
+        /// </summary>
+        /// <param name="name">The name of the histogram.</param>
+        /// <param name="unit">The optional unit of measurement for the values recorded by the histogram.</param>
+        /// <param name="description">The optional description of the histogram.</param>
+        protected MetricHistogram(string name, string? unit = null, string? description = null)
+            : this(new(name, unit, description))
+        {
+        }
+
         /// <summary>
         /// Record the given value on the histogram.
         /// </summary>