[release-2.10] refactor: autofill if post is published but no publish…

… time (#4781)

This is an automated cherry-pick of #4775

/assign ruibaby

```release-note
修复文章可能因为没有发布时间导致发布失败的问题。
```

application/src/main/java/run/halo/app/core/extension/reconciler/PostReconciler.java

@@ -113,6 +113,10 @@ public Result reconcile(Request request) {
                     post.setStatus(status);
                 }
 
+                if (post.isPublished() && post.getSpec().getPublishTime() == null) {
+                    post.getSpec().setPublishTime(Instant.now());
+                }
+
                 // calculate the sha256sum
                 var configSha256sum = Hashing.sha256().hashString(post.getSpec().toString(), UTF_8)
                         .toString();

application/src/main/java/run/halo/app/core/extension/reconciler/SinglePageReconciler.java

@@ -112,6 +112,10 @@ void subscribeNewCommentNotification(SinglePage page) {
 
     private void reconcileSpec(String name) {
         client.fetch(SinglePage.class, name).ifPresent(page -> {
+            if (page.isPublished() && page.getSpec().getPublishTime() == null) {
+                page.getSpec().setPublishTime(Instant.now());
+            }
+
             // un-publish if necessary
             if (page.isPublished() && Objects.equals(false, page.getSpec().getPublish())) {
                 unPublish(name);