Inviting users to a workspace

As opposed to directly adding a user to a workspace, the user can be invited to join if she pleases.

For a workspace admin to invite a user, it means to go to the Workspace Membership Management section (WIKITHREEDOTO-24) and use the auto-suggest box, type in the user's name, click Invite, fill in the invite message or leave the default and press Send.

Once the invitation is sent, a message is sent to the user and the invitation is stored in the workspace's group page (as an XWiki object) until:
a) The user accepts the invitation
b) The workspace admin deletes the invitation, invalidating it.

The invited user receives a message with the invitation message and a link to join the workspace.
When the user visits the workspace's dashboard, if she is not yet a member but has an ongoing invitation, a message will inform the user that she is invited to join that group. Whether or not it is a private group, the user can immediately join it by pressing the Join button.