Make headers in ExecuteNexusOperationInput case insensitive (#2342)

* Make headers in ExecuteNexusOperationInput case insensitive

* Ensure all headers sent are lower case

* run spotless

Author: Quinn-With-Two-Ns

temporal-sdk/src/main/java/io/temporal/common/interceptors/WorkflowOutboundCallsInterceptor.java

@@ -33,6 +33,7 @@
 import java.util.*;
 import java.util.function.BiPredicate;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 import javax.annotation.Nullable;
 
 /**
@@ -285,7 +286,14 @@ public ExecuteNexusOperationInput(
       this.resultType = resultType;
       this.arg = arg;
       this.options = options;
-      this.headers = headers;
+      this.headers =
+          headers.entrySet().stream()
+              .collect(
+                  Collectors.toMap(
+                      (k) -> k.getKey().toLowerCase(),
+                      Map.Entry::getValue,
+                      (a, b) -> a,
+                      () -> new TreeMap<>(String.CASE_INSENSITIVE_ORDER)));
     }
 
     public String getService() {
@@ -316,6 +324,10 @@ public NexusOperationOptions getOptions() {
       return options;
     }
 
+    /**
+     * Get headers that will be sent with the request. The returned map operates without regard to
+     * case.
+     */
     public Map<String, String> getHeaders() {
       return headers;
     }

temporal-sdk/src/main/java/io/temporal/internal/sync/SyncWorkflowContext.java

@@ -816,7 +816,8 @@ public <R> ExecuteNexusOperationOutput<R> executeNexusOperation(
     attributes.setOperation(input.getOperation());
     attributes.setService(input.getService());
     attributes.setEndpoint(input.getEndpoint());
-    attributes.putAllNexusHeader(input.getHeaders());
+    // Ensure that the headers are lowercase
+    input.getHeaders().forEach((k, v) -> attributes.putNexusHeader(k.toLowerCase(), v));
     attributes.setScheduleToCloseTimeout(
         ProtobufTimeUtils.toProtoDuration(input.getOptions().getScheduleToCloseTimeout()));