Adds logger to OtlpMetricExporter init so GRPC calls can be logged.

Author: BennettSmith

Sources/Exporters/OpenTelemetryProtocol/metric/OtlpMetricExporter.swift

@@ -4,6 +4,7 @@
  */
 
 import Foundation
+import Logging
 import GRPC
 import NIO
 import NIOHPACK
@@ -18,15 +19,18 @@ public class OtlpMetricExporter: MetricExporter {
 
 
 
-    public init(channel: GRPCChannel, config: OtlpConfiguration = OtlpConfiguration()) {
+    public init(channel: GRPCChannel, config: OtlpConfiguration = OtlpConfiguration(), logger: Logger = Logger(label: "io.grpc", factory: { _ in SwiftLogNoOpLogHandler() })) {
         self.channel = channel
         self.config = config
         self.metricClient = Opentelemetry_Proto_Collector_Metrics_V1_MetricsServiceClient(channel: self.channel)
 
         if let headers = EnvVarHeaders.attributes {
-            callOptions = CallOptions(customMetadata: HPACKHeaders(headers))
+            callOptions = CallOptions(customMetadata: HPACKHeaders(headers), logger: logger)
         } else if let headers = config.headers {
-            callOptions = CallOptions(customMetadata: HPACKHeaders(headers))
+            callOptions = CallOptions(customMetadata: HPACKHeaders(headers), logger: logger)
+        }
+        else {
+            callOptions = CallOptions(logger: logger)
         }
     }