[FSSDK-11953] java-sdk CMAB: Fix missing bucketing reasons in CMAB decision path (#592)

* Initial plan

* Fix missing CMAB bucketing reasons in decision process

Added merge of bucketing reasons for CMAB experiments to ensure traffic allocation information is included in decision responses.

Co-authored-by: Mat001 <1386553+Mat001@users.noreply.github.com>

* fix: missing decision reasons added in cmab flow

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Mat001 <1386553+Mat001@users.noreply.github.com>
Co-authored-by: Matjaz Pirnovar <Mat001@users.noreply.github.com>
Co-authored-by: FarhanAnjum-opti <farhan.anjum@optimizely.com>

Author: 3 people

core-api/src/main/java/com/optimizely/ab/bucketing/DecisionService.java

@@ -172,9 +172,10 @@ public DecisionResponse<Variation> getVariation(@Nonnull Experiment experiment,
             String bucketingId = getBucketingId(user.getUserId(), user.getAttributes());
             String cmabUuid = null;
             decisionVariation = bucketer.bucket(experiment, bucketingId, projectConfig, decisionPath);
+            reasons.merge(decisionVariation.getReasons());
             if (decisionPath == DecisionPath.WITH_CMAB && isCmabExperiment(experiment) && decisionVariation.getResult() != null) {
                 // group-allocation and traffic-allocation checking passed for cmab  
-                // we need server decision overruling local bucketing for cmab  
+                // we need server decision overruling local bucketing for cmab
                 DecisionResponse<CmabDecision> cmabDecision = getDecisionForCmabExperiment(projectConfig, experiment, user, bucketingId, options);
                 reasons.merge(cmabDecision.getReasons());
 
@@ -197,7 +198,6 @@ public DecisionResponse<Variation> getVariation(@Nonnull Experiment experiment,
                 }
             } else {
                 // Standard bucketing for non-CMAB experiments
-                reasons.merge(decisionVariation.getReasons());
                 variation = decisionVariation.getResult();
             }