Fix error message wording for PutObjectLockConfig (#8759)

Co-Authored-By: kannappanr <30541348+kannappanr@users.noreply.github.com>
Co-authored-by: Harshavardhana <harsha@minio.io>

cmd/api-errors.go

@@ -143,6 +143,7 @@ const (
 	ErrBadRequest
 	ErrKeyTooLongError
 	ErrInvalidBucketObjectLockConfiguration
+	ErrObjectLockConfigurationNotAllowed
 	ErrObjectLocked
 	ErrInvalidRetentionDate
 	ErrPastObjectLockRetainDate
@@ -732,6 +733,11 @@ var errorCodes = errorCodeMap{
 		Description:    "Bucket is missing ObjectLockConfiguration",
 		HTTPStatusCode: http.StatusBadRequest,
 	},
+	ErrObjectLockConfigurationNotAllowed: {
+		Code:           "InvalidBucketState",
+		Description:    "Object Lock configuration cannot be enabled on existing buckets.",
+		HTTPStatusCode: http.StatusConflict,
+	},
 	ErrObjectLocked: {
 		Code:           "InvalidRequest",
 		Description:    "Object is WORM protected and cannot be overwritten",

cmd/bucket-handlers.go

@@ -1017,7 +1017,7 @@ func (api objectAPIHandlers) PutBucketObjectLockConfigHandler(w http.ResponseWri
 	if err != nil {
 		aerr := toAPIError(ctx, err)
 		if err == errConfigNotFound {
-			aerr = errorCodes.ToAPIErr(ErrMethodNotAllowed)
+			aerr = errorCodes.ToAPIErr(ErrObjectLockConfigurationNotAllowed)
 		}
 		writeErrorResponse(ctx, w, aerr, r.URL, guessIsBrowserReq(r))
 		return