refactor(documents): bundle density filters into a record (#385)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/document/DensityFilters.java

@@ -0,0 +1,23 @@
+package org.raddatz.familienarchiv.document;
+
+import org.raddatz.familienarchiv.tag.TagOperator;
+
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * The non-date filters honoured by {@link DocumentService#getDensity(DensityFilters)}.
+ * Date bounds (from/to) are deliberately excluded — see the service Javadoc for why.
+ *
+ * Kept as a record so the seven values are passed as one named bundle instead of a
+ * positional argument list where two UUIDs (sender vs. receiver) can be swapped by
+ * accident at the call site.
+ */
+public record DensityFilters(
+        String text,
+        UUID sender,
+        UUID receiver,
+        List<String> tags,
+        String tagQ,
+        DocumentStatus status,
+        TagOperator tagOperator) {}

backend/src/main/java/org/raddatz/familienarchiv/document/DocumentController.java

@@ -401,7 +401,7 @@ public class DocumentController {
             @Parameter(description = "Tag operator: AND (default) or OR") @RequestParam(required = false) String tagOp) {
         TagOperator operator = "OR".equalsIgnoreCase(tagOp) ? TagOperator.OR : TagOperator.AND;
         DocumentDensityResult result = documentService.getDensity(
-                q, senderId, receiverId, tags, tagQ, status, operator);
+                new DensityFilters(q, senderId, receiverId, tags, tagQ, status, operator));
         return ResponseEntity.ok()
                 .cacheControl(CacheControl.maxAge(5, TimeUnit.MINUTES).cachePrivate())
                 .body(result);

backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java

@@ -146,10 +146,8 @@ public class DocumentService {
      * 'YYYY-MM')) and accept that the criteria/specification surface needs a
      * parallel native-query path.
      */
-    public DocumentDensityResult getDensity(
-            String text, UUID sender, UUID receiver,
-            List<String> tags, String tagQ,
-            DocumentStatus status, TagOperator tagOperator) {
+    public DocumentDensityResult getDensity(DensityFilters filters) {
+        String text = filters.text();
         boolean hasText = StringUtils.hasText(text);
         List<UUID> rankedIds = null;
         if (hasText) {
@@ -160,7 +158,9 @@ public class DocumentService {
         }
         Specification<Document> spec = buildSearchSpec(
                 hasText, rankedIds, null, null,
-                sender, receiver, tags, tagQ, status, tagOperator);
+                filters.sender(), filters.receiver(),
+                filters.tags(), filters.tagQ(),
+                filters.status(), filters.tagOperator());
 
         List<LocalDate> dates = documentRepository.findAll(spec).stream()
                 .map(Document::getDocumentDate)