Fixed bug around channel file sidebar (#27705)

* Fixed the issue for DB layer, ES to go

* Handled channel bookmarks

* Handled Bleve

* Lint fix

* Added channel bookmark test

* Skip bleve test

* Used common function

* SKipping ES as indexing logic in unavailable in test

server/public/model/post.go

@@ -260,6 +260,22 @@ type FileForIndexing struct {
 	Content   string `json:"content"`
 }
 
+// ShouldIndex tells if a file should be indexed or not.
+// index files which are-
+// a. not deleted
+// b. have an associated post ID, if no post ID, then,
+// b.i. the file should belong to the channel's bookmarks, as indicated by the "CreatorId" field.
+//
+// Files not passing this criteria will be deleted from ES index.
+// We're deleting those files from ES index instead of simply skipping them while fetching a batch of files
+// because existing ES indexes might have these files already indexed, so we need to remove them from index.
+func (file *FileForIndexing) ShouldIndex() bool {
+	// NOTE - this function is used in server as well as Enterprise code.
+	// Make sure to update public package dependency in both server and Enterprise code when
+	// updating the logic here and to test both places.
+	return file != nil && file.DeleteAt == 0 && (file.PostId != "" || file.CreatorId == BookmarkFileOwner)
+}
+
 // ShallowCopy is an utility function to shallow copy a Post to the given
 // destination without touching the internal RWMutex.
 func (o *Post) ShallowCopy(dst *Post) error {