Resolve "Add a contact mail field to the patient model"

What does this MR do?

Adds a contact mail for each patient, also updates the pages that show information on patients (/view, /edit, and /add).

Does not check whether the mail address is valid or not.

Does this MR meet the acceptance criteria?

• I have added tests to validate the new functionality.
• I have updated the documentation accordingly.

Closes #80 (closed)