Add ObjectTagging Support (#8754)

This PR adds support for AWS S3 ObjectTagging API as explained here
https://docs.aws.amazon.com/AmazonS3/latest/dev/object-tagging.html

cmd/api-errors.go

@@ -36,6 +36,7 @@ import (
 	"github.com/minio/minio/pkg/hash"
 	"github.com/minio/minio/pkg/objectlock"
 	"github.com/minio/minio/pkg/policy"
+	"github.com/minio/minio/pkg/tagging"
 )
 
 // APIError structure
@@ -150,6 +151,7 @@ const (
 	ErrPastObjectLockRetainDate
 	ErrUnknownWORMModeDirective
 	ErrObjectLockInvalidHeaders
+	ErrInvalidTagDirective
 	// Add new error codes here.
 
 	// SSE-S3 related API errors
@@ -830,6 +832,11 @@ var errorCodes = errorCodeMap{
 		Description:    "Your metadata headers exceed the maximum allowed metadata size.",
 		HTTPStatusCode: http.StatusBadRequest,
 	},
+	ErrInvalidTagDirective: {
+		Code:           "InvalidArgument",
+		Description:    "Unknown tag directive.",
+		HTTPStatusCode: http.StatusBadRequest,
+	},
 	ErrInvalidEncryptionMethod: {
 		Code:           "InvalidRequest",
 		Description:    "The encryption method specified is not supported",
@@ -1780,6 +1787,12 @@ func toAPIError(ctx context.Context, err error) APIError {
 		// their internal error types. This code is only
 		// useful with gateway implementations.
 		switch e := err.(type) {
+		case tagging.Error:
+			apiErr = APIError{
+				Code:           "InvalidTag",
+				Description:    e.Error(),
+				HTTPStatusCode: http.StatusBadRequest,
+			}
 		case policy.Error:
 			apiErr = APIError{
 				Code:           "MalformedPolicy",