set global headers earlier when preparing request (#3000)

Author: amaskara-dd

.generator/src/generator/templates/client.j2

@@ -232,6 +232,13 @@ func (c *APIClient) PrepareRequest(
 
 	var body *bytes.Buffer
 
+	// Apply default headers unless they are overridden
+	for header, value := range c.Cfg.DefaultHeader {
+		if _, exists := headerParams[header]; !exists {
+			headerParams[header] = value
+		}
+	}
+
 	// Detect postBody type and post.
 	if postBody != nil {
 		contentType := headerParams["Content-Type"]
@@ -401,10 +408,6 @@ func (c *APIClient) PrepareRequest(
 		}
 	}
 
-	for header, value := range c.Cfg.DefaultHeader {
-		localVarRequest.Header.Add(header, value)
-	}
-
 	if !c.Cfg.Compress {
 		// gzip is on by default, so disable it by setting encoding to identity
 		localVarRequest.Header.Add("Accept-Encoding", "identity")

api/datadog/client.go

@@ -232,6 +232,13 @@ func (c *APIClient) PrepareRequest(
 
 	var body *bytes.Buffer
 
+	// Apply default headers unless they are overridden
+	for header, value := range c.Cfg.DefaultHeader {
+		if _, exists := headerParams[header]; !exists {
+			headerParams[header] = value
+		}
+	}
+
 	// Detect postBody type and post.
 	if postBody != nil {
 		contentType := headerParams["Content-Type"]
@@ -401,10 +408,6 @@ func (c *APIClient) PrepareRequest(
 		}
 	}
 
-	for header, value := range c.Cfg.DefaultHeader {
-		localVarRequest.Header.Add(header, value)
-	}
-
 	if !c.Cfg.Compress {
 		// gzip is on by default, so disable it by setting encoding to identity
 		localVarRequest.Header.Add("Accept-Encoding", "identity")