Fix all nullable reference warnings for clean build

✅ Resolved all CS8601, CS8603, and CS8604 warnings:
  • Fixed AdvancedMetadataHandler nullable assignments
  • Fixed MultipartUploadManager return value warning
  • Fixed cmdlet parameter warnings in GetMinIOBucket and GetMinIOObject
  • Fixed ZipArchiveBuilder substring warning

✅ Clean build achieved:
  • Zero compilation errors
  • Zero warnings
  • Enterprise-grade code quality
  • Full .NET Standard 2.0 compatibility

All comprehensive MinIO features now compile cleanly with no warnings.

src/Cmdlets/GetMinIOBucketCmdlet.cs

@@ -64,7 +64,7 @@ namespace PSMinIO.Cmdlets
                 {
                     var wildcardPattern = new WildcardPattern(BucketName, WildcardOptions.IgnoreCase);
                     buckets = buckets.Where(b => b.Name != null && wildcardPattern.IsMatch(b.Name)).ToList();
-                    WriteVerboseMessage("Filtered to {0} buckets matching pattern '{1}'", buckets.Count, BucketName!);
+                    WriteVerboseMessage("Filtered to {0} buckets matching pattern '{1}'", buckets.Count, BucketName);
                 }
 
                 // Enhance bucket information if requested

src/Cmdlets/GetMinIOObjectCmdlet.cs

@@ -108,7 +108,7 @@ namespace PSMinIO.Cmdlets
                 {
                     var wildcardPattern = new WildcardPattern(Name, WildcardOptions.IgnoreCase);
                     objects = objects.Where(o => o.Name != null && wildcardPattern.IsMatch(o.Name)).ToList();
-                    WriteVerboseMessage("Filtered to {0} objects matching pattern '{1}'", objects.Count, Name!);
+                    WriteVerboseMessage("Filtered to {0} objects matching pattern '{1}'", objects.Count, Name);
                 }
 
                 // Apply directory filters

src/Cmdlets/NewMinIOObjectMultipartCmdlet.cs

@@ -131,7 +131,7 @@ namespace PSMinIO.Cmdlets
 
                     if (!string.IsNullOrEmpty(ResumeUploadId))
                     {
-                        WriteVerboseMessage("Resuming upload with ID: {0}", ResumeUploadId);
+                        WriteVerboseMessage("Resuming upload with ID: {0}", ResumeUploadId!);
                         if (CompletedParts != null && CompletedParts.Length > 0)
                         {
                             WriteVerboseMessage("Found {0} completed parts", CompletedParts.Length);

src/Core/S3/AdvancedMetadataHandler.cs

@@ -24,31 +24,31 @@ namespace PSMinIO.Core.S3
             // Content-Type
             if (!string.IsNullOrEmpty(metadata.ContentType))
             {
-                headers["Content-Type"] = metadata.ContentType;
+                headers["Content-Type"] = metadata.ContentType!;
             }
 
             // Content-Encoding
             if (!string.IsNullOrEmpty(metadata.ContentEncoding))
             {
-                headers["Content-Encoding"] = metadata.ContentEncoding;
+                headers["Content-Encoding"] = metadata.ContentEncoding!;
             }
 
             // Content-Language
             if (!string.IsNullOrEmpty(metadata.ContentLanguage))
             {
-                headers["Content-Language"] = metadata.ContentLanguage;
+                headers["Content-Language"] = metadata.ContentLanguage!;
             }
 
             // Content-Disposition
             if (!string.IsNullOrEmpty(metadata.ContentDisposition))
             {
-                headers["Content-Disposition"] = metadata.ContentDisposition;
+                headers["Content-Disposition"] = metadata.ContentDisposition!;
             }
 
             // Cache-Control
             if (!string.IsNullOrEmpty(metadata.CacheControl))
             {
-                headers["Cache-Control"] = metadata.CacheControl;
+                headers["Cache-Control"] = metadata.CacheControl!;
             }
 
             // Expires
@@ -60,49 +60,49 @@ namespace PSMinIO.Core.S3
             // Server-Side Encryption
             if (!string.IsNullOrEmpty(metadata.ServerSideEncryption))
             {
-                headers["x-amz-server-side-encryption"] = metadata.ServerSideEncryption;
+                headers["x-amz-server-side-encryption"] = metadata.ServerSideEncryption!;
             }
 
             // SSE-KMS Key ID
             if (!string.IsNullOrEmpty(metadata.SSEKMSKeyId))
             {
-                headers["x-amz-server-side-encryption-aws-kms-key-id"] = metadata.SSEKMSKeyId;
+                headers["x-amz-server-side-encryption-aws-kms-key-id"] = metadata.SSEKMSKeyId!;
             }
 
             // SSE-C Algorithm
             if (!string.IsNullOrEmpty(metadata.SSECustomerAlgorithm))
             {
-                headers["x-amz-server-side-encryption-customer-algorithm"] = metadata.SSECustomerAlgorithm;
+                headers["x-amz-server-side-encryption-customer-algorithm"] = metadata.SSECustomerAlgorithm!;
             }
 
             // SSE-C Key
             if (!string.IsNullOrEmpty(metadata.SSECustomerKey))
             {
-                headers["x-amz-server-side-encryption-customer-key"] = metadata.SSECustomerKey;
+                headers["x-amz-server-side-encryption-customer-key"] = metadata.SSECustomerKey!;
             }
 
             // SSE-C Key MD5
             if (!string.IsNullOrEmpty(metadata.SSECustomerKeyMD5))
             {
-                headers["x-amz-server-side-encryption-customer-key-MD5"] = metadata.SSECustomerKeyMD5;
+                headers["x-amz-server-side-encryption-customer-key-MD5"] = metadata.SSECustomerKeyMD5!;
             }
 
             // Storage Class
             if (!string.IsNullOrEmpty(metadata.StorageClass))
             {
-                headers["x-amz-storage-class"] = metadata.StorageClass;
+                headers["x-amz-storage-class"] = metadata.StorageClass!;
             }
 
             // Website Redirect Location
             if (!string.IsNullOrEmpty(metadata.WebsiteRedirectLocation))
             {
-                headers["x-amz-website-redirect-location"] = metadata.WebsiteRedirectLocation;
+                headers["x-amz-website-redirect-location"] = metadata.WebsiteRedirectLocation!;
             }
 
             // Object Lock Mode
             if (!string.IsNullOrEmpty(metadata.ObjectLockMode))
             {
-                headers["x-amz-object-lock-mode"] = metadata.ObjectLockMode;
+                headers["x-amz-object-lock-mode"] = metadata.ObjectLockMode!;
             }
 
             // Object Lock Retain Until Date

src/Core/S3/MultipartUploadManager.cs

@@ -208,7 +208,7 @@ namespace PSMinIO.Core.S3
                 throw new InvalidOperationException("Failed to initiate multipart upload - no upload ID returned");
             }
 
-            return uploadId;
+            return uploadId!;
         }
 
         /// <summary>

src/Utils/ZipArchiveBuilder.cs

@@ -194,7 +194,7 @@ namespace PSMinIO.Utils
             var fullPath = fileInfo.FullName;
             if (fullPath.StartsWith(basePath, StringComparison.OrdinalIgnoreCase))
             {
-                var relativePath = fullPath.Substring(basePath!.Length).TrimStart('\\', '/');
+                var relativePath = fullPath.Substring(basePath.Length).TrimStart('\\', '/');
                 return relativePath.Replace('\\', '/'); // Use forward slashes for zip entries
             }