FIX: Increase time of DOWNLOAD_URL_EXPIRES_AFTER_SECONDS to 5 minutes (#10160)

* Change S3Helper::DOWNLOAD_URL_EXPIRES_AFTER_SECONDS to 5 minutes, which controls presigned URL expiry and secure-media route cache time.
* This is done because of the composer preview refreshing while typing causes a lot of requests sent to our server because of the short URL expiry. If this ends up being not enough we can always increase the time or explore other avenues (e.g. GitHub has a 7 day validity for secure URLs)

lib/file_store/s3_store.rb

@@ -168,9 +168,9 @@ module FileStore
       url.sub(File.join("#{schema}#{absolute_base_url}", folder), File.join(SiteSetting.Upload.s3_cdn_url, "/"))
     end
 
-    def signed_url_for_path(path)
+    def signed_url_for_path(path, expires_in: S3Helper::DOWNLOAD_URL_EXPIRES_AFTER_SECONDS)
       key = path.sub(absolute_base_url + "/", "")
-      presigned_url(key)
+      presigned_url(key, expires_in: expires_in)
     end
 
     def cache_avatar(avatar, user_id)
@@ -243,8 +243,14 @@ module FileStore
 
     private
 
-    def presigned_url(url, force_download: false, filename: false)
-      opts = { expires_in: S3Helper::DOWNLOAD_URL_EXPIRES_AFTER_SECONDS }
+    def presigned_url(
+      url,
+      force_download: false,
+      filename: false,
+      expires_in: S3Helper::DOWNLOAD_URL_EXPIRES_AFTER_SECONDS
+    )
+      opts = { expires_in: expires_in }
+
       if force_download && filename
         opts[:response_content_disposition] = ActionDispatch::Http::ContentDisposition.format(
           disposition: "attachment", filename: filename

lib/s3_helper.rb

@@ -8,7 +8,13 @@ class S3Helper
 
   attr_reader :s3_bucket_name, :s3_bucket_folder_path
 
-  DOWNLOAD_URL_EXPIRES_AFTER_SECONDS ||= 15
+  ##
+  # Controls the following:
+  #
+  # * cache time for secure-media URLs
+  # * expiry time for S3 presigned URLs, which include backup downloads and
+  #   any upload that has a private ACL (e.g. secure uploads)
+  DOWNLOAD_URL_EXPIRES_AFTER_SECONDS ||= 300
 
   def initialize(s3_bucket_name, tombstone_prefix = '', options = {})
     @s3_client = options.delete(:client)