features: revoke_license also revoke trial license

Have `revoke_license` revoke the builtin trial license as well for more
convenient testing.

src/v/features/feature_table.cc

@@ -26,6 +26,7 @@
 
 #include <chrono>
 #include <memory>
+#include <optional>
 
 // The feature table is closely related to cluster and uses many types from it
 using namespace cluster;
@@ -717,6 +718,7 @@ void feature_table::set_builtin_trial_license(
   model::timestamp cluster_creation_timestamp) {
     _builtin_trial_license = make_builtin_trial_license(
       model::to_time_point(cluster_creation_timestamp));
+    _builtin_trial_license_initialized = true;
 
     if (ss::this_shard_id() == 0) {
         vlog(
@@ -727,7 +729,10 @@ void feature_table::set_builtin_trial_license(
     }
 }
 
-void feature_table::revoke_license() { _license = std::nullopt; }
+void feature_table::revoke_license() {
+    _license = std::nullopt;
+    _builtin_trial_license = std::nullopt;
+}
 
 const std::optional<security::license>& feature_table::get_license() const {
     return _license ? _license : _builtin_trial_license;
@@ -745,9 +750,9 @@ bool feature_table::should_sanction() const {
         return _builtin_trial_license->is_expired();
     }
 
-    // We are yet to initialize _builtin_trial_license on cluster creation, be
-    // permissive in the meantime
-    return false;
+    // While we are yet to initialize _builtin_trial_license on cluster
+    // creation, be permissive
+    return _builtin_trial_license_initialized;
 }
 
 void feature_table::testing_activate_all() {

src/v/features/feature_table.h

@@ -739,6 +739,10 @@ class feature_table {
     // Built in trial license to fall back to if there is no license set
     std::optional<security::license> _builtin_trial_license;
 
+    // Whether _builtin_trial_license has ever been initialized
+    // Used for implementing revoking the trial license for testing
+    bool _builtin_trial_license_initialized{false};
+
     model::offset _applied_offset{};
 
     // feature_manager is a friend so that they can initialize

src/v/features/tests/feature_table_test.cc

@@ -370,6 +370,10 @@ FIXTURE_TEST(feature_table_trial_license_test, feature_table_fixture) {
     BOOST_CHECK_EQUAL(ft.get_license().has_value(), true);
     BOOST_CHECK_EQUAL(ft.get_license()->is_expired(), false);
     BOOST_CHECK_EQUAL(ft.should_sanction(), false);
+
+    ft.revoke_license();
+    BOOST_CHECK_EQUAL(ft.get_license().has_value(), false);
+    BOOST_CHECK_EQUAL(ft.should_sanction(), true);
 }
 
 SEASTAR_THREAD_TEST_CASE(feature_table_probe_expiry_metric_test) {