feat(campaign): govern attachment reuse

src/govoplan_campaign/backend/messages/builder.py

@@ -19,6 +19,7 @@ from govoplan_campaign.backend.attachments.resolver import (
     effective_send_without_attachments_behavior,
     resolve_entry_attachments,
 )
+from govoplan_campaign.backend.attachments.reuse import evaluate_attachment_reuse
 from govoplan_campaign.backend.campaign.addressing import effective_address_lists, formatted_recipient
 from govoplan_campaign.backend.campaign.entries import load_campaign_entries
 from govoplan_campaign.backend.campaign.field_values import ignored_entry_field_overrides
@@ -1149,6 +1150,28 @@ def _apply_campaign_level_issues(built_messages: list[BuiltMessage], issues: lis
                 status = _apply_behavior(status, issue.behavior)
         built.draft.validation_status = status
 
+
+def _apply_attachment_reuse_policy(
+    config: CampaignConfig,
+    built_messages: list[BuiltMessage],
+) -> dict[str, object]:
+    evaluation = evaluate_attachment_reuse(
+        [built.draft for built in built_messages],
+        policy=config.attachments.reuse_policy,
+    )
+    for built in built_messages:
+        issues = evaluation.issues_by_entry_index.get(built.draft.entry_index, [])
+        if not issues:
+            continue
+        built.draft.issues.extend(issues)
+        for issue in issues:
+            if issue.behavior:
+                built.draft.validation_status = _apply_behavior(
+                    built.draft.validation_status,
+                    issue.behavior,
+                )
+    return evaluation.report
+
 def build_campaign_messages(
     config: CampaignConfig,
     *,
@@ -1203,6 +1226,10 @@ def build_campaign_messages(
         )
         if residual_message is not None:
             built_messages.append(residual_message)
+        attachment_reuse = _apply_attachment_reuse_policy(
+            config,
+            built_messages,
+        )
 
     rules_resolved = sum(len(built.draft.attachments) for built in built_messages)
     report = CampaignBuildReport(
@@ -1216,6 +1243,7 @@ def build_campaign_messages(
             duration_ms=(time.perf_counter() - started) * 1000,
             rules_resolved=rules_resolved,
         ),
+        attachment_reuse=attachment_reuse,
         residual_file_disposition=_residual_file_disposition_evidence(
             config=config,
             residual_groups=residual_groups,