FEATURE: Improving bookmarks part 2 -- Topic Bookmarking (#8954)

### UI Changes

If `SiteSetting.enable_bookmarks_with_reminders` is enabled:

* Clicking "Bookmark" on a topic will create a new Bookmark record instead of a post + user action
* Clicking "Clear Bookmarks" on a topic will delete all the new Bookmark records on a topic
* The topic bookmark buttons control the post bookmark flags correctly and vice-versa
Disabled selecting the "reminder type" for bookmarks in the UI because the backend functionality is not done yet (of sending users notifications etc.)

### Other Changes

* Added delete bookmark route (but no UI yet)
* Added a rake task to sync the old PostAction bookmarks to the new Bookmark table, which can be run as many times as we want for a site (it will not create duplicates).

lib/tasks/bookmarks.rake

@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+require_dependency "rake_helpers"
+
+##
+# This will create records in the new bookmarks table from PostAction
+# records. The task is idempotent, it will not create additional bookmark
+# records for PostActions that have already been created in the new table.
+# You can provide a sync_limit for a smaller batch run.
+#
+desc "migrates old PostAction bookmarks to the new Bookmark model & table"
+task "bookmarks:sync_to_table", [:sync_limit] => :environment do |_t, args|
+  sync_limit = args[:sync_limit] || 0
+  post_action_bookmarks = PostAction
+    .select('post_actions.id', 'post_actions.post_id', 'posts.topic_id', 'post_actions.user_id')
+    .where(post_action_type_id: PostActionType.types[:bookmark])
+    .joins(:post)
+    .where(deleted_at: nil)
+    .joins('LEFT JOIN bookmarks ON bookmarks.post_id = post_actions.post_id AND bookmarks.user_id = post_actions.user_id')
+    .where('bookmarks.id IS NULL')
+
+  # if sync_limit is provided as an argument this will cap
+  # the number of bookmarks that will be created in a run of
+  # this task (for huge bookmark count communities)
+  if sync_limit > 0
+    post_action_bookmarks = post_action_bookmarks.limit(sync_limit)
+  end
+
+  post_action_bookmark_count = post_action_bookmarks.count('post_actions.id')
+  bookmarks_to_create = []
+  i = 0
+
+  Bookmark.transaction do
+    post_action_bookmarks.find_each(batch_size: 1000) do |pab|
+      RakeHelpers.print_status_with_label("Creating post new bookmarks.......", i, post_action_bookmark_count)
+      now = Time.zone.now
+      bookmarks_to_create << {
+        topic_id: pab.topic_id,
+        post_id: pab.post_id,
+        user_id: pab.user_id,
+        created_at: now,
+        updated_at: now
+      }
+
+      i += 1
+    end
+
+    # this will ignore conflicts in the bookmarks table so
+    # if the user already has a post bookmarked in the new way,
+    # then we don't error and keep on truckin'
+    #
+    # we shouldn't have duplicates here at any rate because of
+    # the above LEFT JOIN but best to be safe knowing this
+    # won't blow up
+    Bookmark.insert_all(bookmarks_to_create)
+  end
+
+  RakeHelpers.print_status_with_label("Bookmark creation complete!            ", i, post_action_bookmark_count)
+  puts ""
+end