Figure out JSON for math problem description

[qgolsteyn]

Description

Figure out the shape of the math problems when send them to the client. We need to figure out the shape of the JSON, as well as the shape of the problem and solution string template. This also mean we need to agree on what data the client needs, in addition to the problem and solution string.

Dependencies

Depends on #9 as the format of the math problem/solution is important for their visualization

Acceptance criteria

• Figure the data needed by the client
• Identify the best shape for the problem and solution string
• Identify the best shape for the JSON payload