Jabber is not widely used these days so message_jabber has been removed
from Moodle core.

Final deprecation of:
- can_post_message
- get_individual_conversations_between_users

The `page_type_list` method for the message component was deprecated
in 5b0769db as part of MDL-54744. However it is still required when
trying to configure blocks on any messaging pages.

Add upgrade step to remove existing orphaned records.

New field to store custom data for message processors.

Added new MESSAGE_CONVERSATION_TYPE_SELF type for self-conversations
and upgraded legacy self-conversations to the new type, removing
repeated members in the message_conversation_members table.
Besides, from now, a self-conversation will be created by default for
all the existing users.

All the self-conversations have been also starred and a default message
will be displayed always to explain how to use them.

A note has been made to remove these and other functions once we
remove the old UI.

This function has been deprecated and no other function has been
added to replace it. It was only called from can_post_message, so
its code has been moved there.

Add new messaging profile preferences to allow users to choose who
can message them:
- By default, users can select between 'My contacts only' and 'My
contacts and anyone in my courses'
- When $CFG->messagingallusers is enabled, a new option is displayed
also: 'Anyone on the site'. For users who have selected this option,
if $CFG->messagingallusers is disabled, the behaviour will be changed
to 'My contacts and anyone in my courses'

Also -

1) Made note of the deprecation as well as the functions and
   files that were removed earlier in upgrade.txt.
2) Added new functions to api.php to replace the deprecated ones
   that were being used in unit tests.
3) Removed files that are no longer being used.

This is used by messaging system for sending/receiving message
to/from noreply or support user. message_send api will now use
core_user class to get noreply or support user and then
send/receive message depending on user state.

MDL-30260 message: added /message/upgrade.txt, checked calls to message_send() are supplying user.emailstop and improved message_send() to handle message requests that don't