feat(flagd-api-testkit): add disabled flag e2e scenarios

Signed-off-by: Jonathan Norris <jonathan.norris@dynatrace.com>

Author: jonathannorris

tools/flagd-api-testkit/src/main/java/dev/openfeature/contrib/tools/flagd/api/testkit/EvaluationSteps.java

@@ -97,6 +97,12 @@ public void resolvedValueEquals(String value) throws IOException {
         assertThat(state.evaluation.getValue()).isEqualTo(EvaluatorUtils.convert(value, state.flagType));
     }
 
+    /** Asserts the resolved value is absent (null) — used for disabled flags where the evaluator omits the value. */
+    @Then("the resolved value should be absent")
+    public void resolvedValueIsAbsent() {
+        assertThat(state.evaluation.getValue()).isNull();
+    }
+
     /** Asserts the evaluation reason matches the expected value. */
     @Then("the reason should be {string}")
     public void reasonEquals(String reason) {