This files describes API changes in /message/ messaging system,
information provided here is intended especially for developers.

=== 3.5 ===

* Changed the database structure so there are no longer two tables for messages, with the only
  difference being that one stores read messages. The 'message' and 'message_read' tables are
  still present in core but will no longer be populated by core APIs. The data will be
  transferred to the new database structure via an ad-hoc task. Please be patient. This can
  take time.
  The new database structure is as follows -
  'messages' - Stores the messages with a 'useridfrom' field specifying the user who sent the
               message and a 'conversationid' field specifying which conversation it is for.
  'message_conversations' - The list of conversations.
  'message_conversation_members' - The list of users in each conversation.
  'message_user_actions' - The list of user actions against a message, eg. read/deleted.
  'notifications' - This has a very similar structure to the old table 'message' and still
                    has a one-to-one relation between users.
  Due to these huge differences the events message_sent, message_deleted and message_viewed
  have changed quite a lot. Please, if you have any observers or are triggering these events
  in your code you will have to make some changes!
* The webservice external function 'core_message_mark_message_read' now only marks messages as
  read, and not notifications. A new external function 'core_message_mark_notification_read' was
  added to mark notifications as read.
* Deprecated the following functions.
  - message_move_userfrom_unread2read
  - message_get_blocked_users
  - message_get_contacts
  - message_mark_message_read
  - message_can_delete_message
  - message_delete_message
  - \core_message\api::mark_all_read_for_user
  Please see their declaration in lib/deprecatedlib.php to view their alternatives (if applicable).
* Final deprecation of the following functions.
  - message_get_recent_notifications
  - message_search
  - message_get_history
  - message_get_recent_conversations
* Added new events for when a notification is sent and viewed.
* Removed the database table 'message_working'. The 'message_working' table was introduced when
  the messaging system was first introduced in Moodle, so, a long time ago. It was never necessary.
* Replaced the usage of the table 'message_popup' to a new table 'message_popup_notifications'.

=== 3.2 ===

* Removed all message_print_* functions as well as the files search.html, search_advanced.html and
  send_form.php due to messaging UI rehaul.
* Deprecated the following functions as they are no longer used.
    - message_get_course_contexts
    - message_remove_url_params
    - message_count_messages
    - message_count_blocked_users
    - message_contact_link
    - message_get_recent_notifications
    - message_history_link
    - message_search
    - message_shorten_message
    - message_get_fragment
    - message_get_history
    - message_get_contact_add_remove_link
    - message_get_contact_block_link
    - message_mark_messages_read
    - message_page_type_list
    - message_can_post_message
    - message_is_user_non_contact_blocked
    - message_is_user_blocked

=== 3.1 ===
* get_message_processors accepts an addition parameter for testing, which will just reset processor and exit.
* Deprecated method message_current_user_is_involved() has been removed.

=== 2.9 ===
* Renderer method \core_message_renderer::manage_messagingoptions now accepts a user id parameter as well.

=== 2.6 ===
* Message processor extending message_output, should return true in can_send_to_any_users()
  if it supports message sending to internal (noreply/support) users.
* Message API has been changed to allow attachments. Message processors that can support
  attachments can now use additional parameter as a part of $eventdata. To send attachments,
  $eventdata should contain properties called "attachment" (must be stored_file) and
  "attachname" (string). Currently, email message processor is the only one to support
  attachments.

=== 2.2 ===

required changes:
* lib/messagelib.php message_send($eventdata)
  $eventdata->userto should contain a property called "emailstop", $eventdata->userto->emailstop
  If it is absent it will be retrieved from the user table causing an additional database query
