Extend competitions winners download fields

[giohappy]

The CSV for winners must include:

• user.username
• user.first_name
• user.last_name
• user.email
• user.phone_number
• user.age
• competition.name
• competition.start_date
• competition.end_date
• competition.age_groups
• prize.name
• prize.sponsor

The bold fields must be added to the output.