feat: Parse JWT exp claim from token in AuthProperties

- Implement robust Base64UrlDecode in TransformUtil using unsigned integers to avoid undefined behavior.
- Update AuthProperties::FromProperties to parse the JWT exp claim from the token and set expires_at_millis_.
- Add expires_at_millis() getter to AuthProperties.
- Add unit tests for Base64UrlDecode and JWT expiration parsing.
- Improve HasValue matcher to support non-matcher arguments and fix MSVC template issues by using SafeMatcherCast and DescribeMatcher.

Co-authored-by: wgtmac <4684607+wgtmac@users.noreply.github.com>

Author: google-labs-jules[bot]

src/iceberg/test/matchers.h

@@ -124,12 +124,14 @@ class HasValueMatcher {
 
   void DescribeTo(std::ostream* os) const {
     *os << "has a value that ";
-    matcher_.DescribeTo(os);
+    ::testing::internal::DescribeMatcher<const typename MatcherT::value_type&>(
+        matcher_, os);
   }
 
   void DescribeNegationTo(std::ostream* os) const {
     *os << "does not have a value that ";
-    matcher_.DescribeTo(os);
+    ::testing::internal::DescribeMatcher<const typename MatcherT::value_type&>(
+        matcher_, os);
   }
 
  private:
@@ -140,7 +142,9 @@ class HasValueMatcher {
 template <typename MatcherT>
 auto HasValue(MatcherT&& matcher) {
   return ::testing::MakePolymorphicMatcher(
-      HasValueMatcher<std::remove_cvref_t<MatcherT>>(std::forward<MatcherT>(matcher)));
+      HasValueMatcher<::testing::Matcher<const std::remove_cvref_t<MatcherT>&>>(
+          ::testing::SafeMatcherCast<const std::remove_cvref_t<MatcherT>&>(
+              std::forward<MatcherT>(matcher))));
 }
 
 // Overload for the common case where we just want to check for presence of any value

src/iceberg/test/transform_util_test.cc

@@ -174,7 +174,8 @@ TEST(TransformUtilTest, Base64UrlDecode) {
   EXPECT_THAT(TransformUtil::Base64UrlDecode("Zm9v"), HasValue(std::string("foo")));
   EXPECT_THAT(TransformUtil::Base64UrlDecode("Zm9vYg"), HasValue(std::string("foob")));
   EXPECT_THAT(TransformUtil::Base64UrlDecode("Zm9vYmE"), HasValue(std::string("fooba")));
-  EXPECT_THAT(TransformUtil::Base64UrlDecode("Zm9vYmFy"), HasValue(std::string("foobar")));
+  EXPECT_THAT(TransformUtil::Base64UrlDecode("Zm9vYmFy"),
+              HasValue(std::string("foobar")));
 
   // Base64Url specific characters
   // "-" -> 62, "_" -> 63