Boards should have an optional description

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User Story

As a user, I want to create a new board with an optional description, so that participants can inform themselves about the content of the board.

Description

Since the boards are displayed with a description on the template and sessions page and no description can be added to boards in the current version, this must be implemented

• The first step is to define the maximum length of the description (number of characters). For example, the description of a board in Miro can only be a maximum of 300 characters long.
• In the backend, the description must be added to the database schema for the board. In addition, all endpoints must be updated so that a description can be specified when creating a board and the description of an existing board can be changed.
• You also need to consider (and possibly create a design draft) whether the description of a board can be changed in the board settings (Settings dialog). If so, a text field for the description must be added to the board settings in the frontend.