Fix various trivial problems (#32861)

1. add/improve comments to help future readers could understand the
problem more easily.
2. add an error log to LDAP with username fallback
3. use `or` instead of `Iif` for "repo/branch_dropdown" (`Iif` was a
mistake, but it doesn't really affect the UI)
4. add `tw-font-mono` style to container digest to match dockerhub
5. fix a bug in RepoBranchTagSelector: the form is not updated when
there is no click to an item

---------

Co-authored-by: delvh <dev.lh@web.de>

web_src/js/components/RepoBranchTagSelector.vue

@@ -113,6 +113,16 @@ const sfc = {
       if (this.menuVisible) this.menuVisible = false;
     });
   },
+
+  mounted() {
+    if (this.refFormActionTemplate) {
+      // if the selector is used in a form and needs to change the form action,
+      // make a mock item and select it to update the form action
+      const item: ListItem = {selected: true, refType: this.currentRefType, refShortName: this.currentRefShortName, rssFeedLink: ''};
+      this.selectItem(item);
+    }
+  },
+
   methods: {
     selectItem(item: ListItem) {
       this.menuVisible = false;