chore[aou-1869]: refactor export bibliograpy endpoint

refactor controller to return a stream instead of string.

Closes: AOU-1869

AoU-Admin/src/main/java/ch/unige/aou/controller/admin/ExportMetadataController.java

@@ -74,7 +74,7 @@ public class ExportMetadataController extends SolidifyController {
   private final IndexResourceService<String, PublicationIndexEntry> indexResourceService;
   private final String indexName;
 
-  public ExportMetadataController(AouProperties aouProperties,QueryBuilderService queryBuilderService,
+  public ExportMetadataController(AouProperties aouProperties, QueryBuilderService queryBuilderService,
           IndexResourceService<String, PublicationIndexEntry> indexResourceService,
           ExportMetadataService exportMetadataService) {
     this.queryBuilderService = queryBuilderService;
@@ -91,7 +91,8 @@ public class ExportMetadataController extends SolidifyController {
           @RequestParam(name = "format") String format) {
 
     ExportFormat exportFormat = ExportFormat.fromValue(format);
-    if (StringTool.isNullOrEmpty(commaSeparatedSearchIds) && StringTool.isNullOrEmpty(commaSeparatedPublicationIds) && StringTool.isNullOrEmpty(searchFrom)) {
+    if (StringTool.isNullOrEmpty(commaSeparatedSearchIds) && StringTool.isNullOrEmpty(commaSeparatedPublicationIds) && StringTool.isNullOrEmpty(
+            searchFrom)) {
       throw new SolidifyHttpErrorException(HttpStatus.BAD_REQUEST, "Either one search id or one publication id or a date is required");
     }
 
@@ -105,7 +106,8 @@ public class ExportMetadataController extends SolidifyController {
       publicationIds.addAll(Arrays.stream(commaSeparatedPublicationIds.split(",")).map(String::trim).toList());
     }
 
-    AouSearchCondition searchConditions = this.queryBuilderService.getSearchesOrPublicationsSearchCondition(searchFrom, searchIds, publicationIds);
+    AouSearchCondition searchConditions = this.queryBuilderService.getSearchesOrPublicationsSearchCondition(searchFrom, searchIds,
+            publicationIds);
 
     List<FacetRequest> facetRequests = new ArrayList<>(); // not interested in facets here
     List<SearchCondition> searchConditionList = this.queryBuilderService.replaceAliasesByIndexField(List.of(searchConditions));
@@ -120,7 +122,7 @@ public class ExportMetadataController extends SolidifyController {
     // convert the string result to Inputstream
     InputStream is = new BufferedInputStream(new ByteArrayInputStream(result.getBytes(StandardCharsets.UTF_8)));
 
-    return this.buildDownloadResponseEntity(is, this.getFileName(exportFormat), extractContentType(exportFormat), 0L);
+    return this.buildDownloadResponseEntity(is, this.getFileName(exportFormat), this.getContentType(exportFormat), 0L);
 
   }
 
@@ -132,7 +134,7 @@ public class ExportMetadataController extends SolidifyController {
     };
   }
 
-  private String extractContentType(ExportFormat format) {
+  private String getContentType(ExportFormat format) {
     return switch (format) {
       case CSV -> "text/csv";
       case XML -> "application/xml";