Added extensions for getting content header values (#2247)

Author: jizc

src/RestSharp/Response/RestResponseExtensions.cs

@@ -22,7 +22,7 @@ public static class RestResponseExtensions {
     /// <param name="headerName">Name of the header</param>
     /// <returns>Header value or null if the header is not found in the response</returns>
     public static string? GetHeaderValue(this RestResponse response, string headerName)
-        => response.Headers?.FirstOrDefault(x => NameIs(x.Name, headerName))?.Value?.ToString();
+        => response.Headers?.FirstOrDefault(x => NameIs(x.Name, headerName))?.Value.ToString();
 
     /// <summary>
     /// Gets all the values of the header with the specified name.
@@ -33,7 +33,29 @@ public static class RestResponseExtensions {
     public static string[] GetHeaderValues(this RestResponse response, string headerName)
         => response.Headers
                 ?.Where(x => NameIs(x.Name, headerName))
-                .Select(x => x.Value?.ToString() ?? "")
+                .Select(x => x.Value.ToString() ?? "")
+                .ToArray() ??
+            [];
+
+    /// <summary>
+    /// Gets the value of the content header with the specified name.
+    /// </summary>
+    /// <param name="response">Response object</param>
+    /// <param name="headerName">Name of the header</param>
+    /// <returns>Header value or null if the content header is not found in the response</returns>
+    public static string? GetContentHeaderValue(this RestResponse response, string headerName)
+        => response.ContentHeaders?.FirstOrDefault(x => NameIs(x.Name, headerName))?.Value.ToString();
+
+    /// <summary>
+    /// Gets all the values of the content header with the specified name.
+    /// </summary>
+    /// <param name="response">Response object</param>
+    /// <param name="headerName">Name of the header</param>
+    /// <returns>Array of header values or empty array if the content header is not found in the response</returns>
+    public static string[] GetContentHeaderValues(this RestResponse response, string headerName)
+        => response.ContentHeaders
+                ?.Where(x => NameIs(x.Name, headerName))
+                .Select(x => x.Value.ToString() ?? "")
                 .ToArray() ??
             [];