Fix feature analysis endpoint (#2437)

Add Transactional annotation to method to fix "no session" error

Author: pieterlukasse

src/main/java/org/ohdsi/webapi/feanalysis/FeAnalysisController.java

@@ -153,6 +153,7 @@ public void deleteAnalysis(@PathParam("id") final Integer feAnalysisId) {
      * @return ID, type, name domain, description, etc of feature analysis
      */
     @GET
+    @Transactional
     @Path("/{id}")
     @Produces(MediaType.APPLICATION_JSON)
     public FeAnalysisDTO getFeAnalysis(@PathParam("id") final Integer feAnalysisId) {

src/main/java/org/ohdsi/webapi/feanalysis/converter/FeAnalysisEntityToFeAnalysisDTOConverter.java

@@ -7,6 +7,7 @@
 import org.ohdsi.webapi.feanalysis.dto.*;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Component;
+import org.hibernate.Hibernate;
 
 import java.util.List;
 import java.util.Objects;
@@ -46,6 +47,7 @@ private Object convertDesignToJson(final FeAnalysisEntity source) {
         switch (source.getType()) {
             case CRITERIA_SET:
                 FeAnalysisWithCriteriaEntity<?> sourceWithCriteria = (FeAnalysisWithCriteriaEntity<?>) source;
+                Hibernate.initialize(sourceWithCriteria.getDesign());  // Explicitly initialize the collection
                 return sourceWithCriteria.getDesign()
                           .stream()
                           .map(this::convertCriteria)