test(flagd): isolate @env-var scenarios from concurrent config reads

@env-var scenarios mutate process-global environment variables (e.g.
FLAGD_SYNC_PORT) that a concurrently-running config-default scenario reads at
build() time, causing intermittent wrong-value assertions (e.g. in-process port
resolving to 9999 instead of 8015). The existing ENV_VARS read-write lock only
serialized @env-var scenarios against each other. Give every scenario in an
engine a READ lock on ENV_VARS (keyed by its include tag); @env-var scenarios
escalate to read-write, so they run exclusively while no other scenario in the
engine reads config.

Signed-off-by: Simon Schrottner <simon.schrottner@gmail.com>

Author: aepfli

providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/e2e/RunE2ETests.java

@@ -101,6 +101,12 @@ private Stream<DynamicNode> resolverTests(String resolverGlue, String includeTag
                 .configurationParameter("cucumber.execution.parallel.config.strategy", "dynamic")
                 .configurationParameter("cucumber.execution.parallel.config.dynamic.factor", "1")
                 .configurationParameter("cucumber.execution.exclusive-resources.env-var.read-write", "ENV_VARS")
+                // Every scenario in this engine carries the include tag, so give them all a READ lock
+                // on ENV_VARS. @env-var scenarios also declare read-write (above) which escalates to an
+                // exclusive lock — so they run while no other scenario in this engine reads config,
+                // preventing a process-global env var (e.g. FLAGD_SYNC_PORT) from leaking into a
+                // concurrent config-default scenario.
+                .configurationParameter("cucumber.execution.exclusive-resources." + includeTag + ".read", "ENV_VARS")
                 .configurationParameter("cucumber.execution.exclusive-resources.grace.read-write", "CONTAINER_RESTART")
                 .build();