Add a /leave command

This is the other side of /join when bookmark_on_join is set to true.

It lets the user easily leave a bookmarked MUC from all of their clients
at once.

doc/source/commands.rst

@@ -426,6 +426,24 @@ MultiUserChat tab commands
         Disconnect you from a room. You can specify an optional
         message.
 
+        This is similar to :term:`/leave`, but keeps the tab open and doesn’t
+        remove the bookmark, so restarting poezio or another client will reopen
+        this room.
+
+    /leave
+        **Usage:** ``/leave [message]``
+
+        Disconnect you from a room, on all of your clients. You can specify an
+        optional message.
+
+        This is similar to :term:`/part`, but closes the tab and removes its
+        bookmark, to make sure we don’t come back to this room the next time we
+        open poezio or another client.
+
+        This is similar to :term:`/close`, but also removes the bookmark to
+        make sure we don’t come back to this room the next time we open poezio
+        or another client.
+
     /nick
         **Usage:** ``/nick <nickname>``
 

poezio/tabs/muctab.py

@@ -1483,6 +1483,17 @@ class MucTab(ChatTab):
             self.refresh()
         self.core.doupdate()
 
+    @command_args_parser.raw
+    def command_leave(self, msg):
+        """
+        /leave [msg]
+        """
+        self.leave_room(msg)
+        if config.get('bookmark_on_join'):
+            self.core.bookmarks.remove(self.jid)
+            self.core.bookmarks.save(self.core.xmpp)
+        self.core.close_tab(self)
+
     @command_args_parser.raw
     def command_close(self, msg):
         """
@@ -2073,6 +2084,13 @@ class MucTab(ChatTab):
                      ' specify an optional message.'),
             'shortdesc':
             'Leave the room.'
+        }, {
+            'name': 'leave',
+            'func': self.command_leave,
+            'usage': '[message]',
+            'desc': ('Disconnect from a room, on all of your clients. '
+                     'You can specify an optional message'),
+            'shortdesc': 'Leave the room.'
         }, {
             'name':
             'close',