AppVeyor Warnings (#403)

* Add size checks before casting to int

Added checks to ensure sizes fit into int before casting.

* Fix windows build without NOMINMAX

---------

Co-authored-by: Dominik Thalhammer <thalhammer.d@googlemail.com>
Co-authored-by: Dominik Thalhammer <dominik@thalhammer.it>

Author: JurgenLB

include/jwt-cpp/jwt.h

@@ -722,13 +722,23 @@ namespace jwt {
 			if (key.substr(0, 27) == "-----BEGIN CERTIFICATE-----") {
 				auto epkey = helper::extract_pubkey_from_cert<error_category>(key, password, ec);
 				if (ec) return {};
-				const int len = static_cast<int>(epkey.size());
+				// Ensure the size fits into an int before casting
+				if (epkey.size() > static_cast<std::size_t>((std::numeric_limits<int>::max)())) {
+					ec = error_category::load_key_bio_write; // Add an appropriate error here
+					return {};
+				}
+				int len = static_cast<int>(epkey.size());
 				if (BIO_write(pubkey_bio.get(), epkey.data(), len) != len) {
 					ec = error_category::load_key_bio_write;
 					return {};
 				}
 			} else {
-				const int len = static_cast<int>(key.size());
+				// Ensure the size fits into an int before casting
+				if (key.size() > static_cast<std::size_t>((std::numeric_limits<int>::max)())) {
+					ec = error_category::load_key_bio_write; // Add an appropriate error here
+					return {};
+				}
+				int len = static_cast<int>(key.size());
 				if (BIO_write(pubkey_bio.get(), key.data(), len) != len) {
 					ec = error_category::load_key_bio_write;
 					return {};