PR#2355 Continued + expanded scope (#2365)

* #2317 Fetch pinned documents once per folder to reduce the number of queries.

* Reorder the lines to keeps const declarations together.

* Add some comments to functions
move pinned document fetch for folder to function
move watched documents per-folder to also function the same
remove unused function in documents model

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Co-authored-by: Błażej Owczarczyk <blazeyy@gmail.com>

server/models/documentSyncQueue.js

@@ -38,6 +38,13 @@ const DocumentSyncQueue = {
     return new Date(Number(new Date()) + queueRecord.staleAfterMs);
   },
 
+  /**
+   * Check if the document can be watched based on the metadata fields
+   * @param {object} metadata - metadata to check
+   * @param {string} metadata.title - title of the document
+   * @param {string} metadata.chunkSource - chunk source of the document
+   * @returns {boolean} - true if the document can be watched, false otherwise
+   */
   canWatch: function ({ title, chunkSource = null } = {}) {
     if (chunkSource.startsWith("link://") && title.endsWith(".html"))
       return true; // If is web-link material (prior to feature most chunkSources were links://)