Add shoe size

One-sentence description

Add shoe size to user profiles

Desired behaviour

We would like to know the shoe size of our members so that we can reserve shoes at the bowling alley and skiing resort without asking for the same information each year.

However, the sizes should be restricted to values between 39 and 47, since there are no smaller/larger shoes at those places. Since not everyone might have a size in this range the field can be empty.

We want to edit the field on the member edit page in the admin and show the shoe size on the public user profiles.

Suggested implementation

New field