Add chat/element/spaces

chat/element/spaces.markdown

+# Spaces
+
+Spaces are a new feature in Matrix/Element to collect rooms together into groups.
+Under the hood spaces are rooms with a special type `m.space` to distinguish them from regular messaging rooms.
+This means spaces (unlike the old communities) are fully decentralized like rooms.
+
+The details are outlined in [MSC1772](https://github.com/matrix-org/matrix-doc/pull/1772).
+
+## Hierarchies
+
+Spaces can contain rooms and members. Since spaces are just rooms, spaces can also contain subspaces.
+This allows to organize rooms in a tree structure.
+
+[[!img /media/chat/element_spaces1.png alt="Element spaces" size="400x"]]
+
+## Types
+
+There are basically 3 types of spaces:
+
+- Public space: An open space for anyone, best for communities
+- Team space: A private space for you and your teammates
+- Private space: A private space to organize your rooms
+
+## Restricted rooms
+
+Within a private (team) space it is now possible to have rooms with a new type of join rule `restricted`.
+A restricted room is like a private room (only invited people can join) and additionally allows to grant
+access to the room based on the membership of a space. This means you can now create a private team space
+and invite teammates to your space. Your teammates will then be able to join all restricted rooms that are
+part of your space without an invite. This greatly simplifies group management when you have a lot of rooms.
+
+Since this introduces some protocol changes, restricted rooms require a new room version (9).
+This means you will have to upgrade your existing rooms to get this feature.
+
+The details are outlined in [MSC3083](https://github.com/matrix-org/matrix-doc/pull/3083).
+
+## Room upgrades
+
+A room upgrade will result in a new room with the upgraded version.
+Existing members will automatically be invited to the new room.
+The older room and messages can still be access via **Room Settings** > **Advanced** > **Room version**.
+
+[[!img /media/chat/element_spaces2.png alt="Element spaces" size="400x"]]
+
+## Creating spaces
+
+Click on the `+` (plus) icon in the space panel on the left and choose a public or private space:
+
+[[!img /media/chat/element_spaces3.png alt="Element spaces" size="400x"]]
+
+If you choose a private space, you will be asked who you are working with - just ignore this.
+We recommend not to try inviting people via email address, since this may not work as expected.
+
+### Public spaces
+
+Public spaces can be joined by anyone without an invite. They also require to set an address
+in the form of `#myspace:phys.ethz.ch` like it is done for public rooms.
+
+Please use some namespacing here, since these public adresses can only be used once.
+
+## Managing spaces
+
+To add rooms and invite people, right click on the space and select **Manage & explore rooms**.
+This will open the space view, from where you can **add** rooms and **invite** others.
+
+You can add existing rooms or directly create new rooms in the space.
+This will by default create a restricted room (visible to space members):
+
+[[!img /media/chat/element_spaces4.png alt="Element spaces" size="400x"]]
+
+If you add an existing room and would like to set the access to restricted,
+open **Room settings** > **Security & Privacy** > **Access** and select **Space members**.
+
+[[!img /media/chat/element_spaces5.png alt="Element spaces" size="400x"]]
+
+## Migrating communities
+
+The old communities are hidden, but community admins can migrate them to spaces.
+
+Open **Settings** > **All settings** > **Preferences** > **Communities** > **Show my communities**
+and click on **Create Space**, which will guide you through the migration process:
+
+[[!img /media/chat/element_spaces6.png alt="Element spaces" size="400x"]]
+
+For further steps see **Managing spaces** above.