player:
{
	_id:
	first_name: 'a',
	last_name: 'b',
	brought_equipment: ['x', 'y', 'z'],
	telephone: 111222333,
	e_mail: 'qwe@gmail.com',
	country: 'x',
	game: 'y', 
	team: 'z' 
}

tournament:
{
	_id: ,
	name: 'a',
	game: 'b',
	oganizers: [
		{
			name: 'a',
			country 'b',
		},

			.
			.
			.
		{
			name: 'x',
			country 'y',
		}
	],
	sponsors: ['a', 'b', 'c'],
	qualified_teams: ['x', 'y', 'z'],
	tournament_type: 'a',
	prize: 3589510,
	start_date: Date(),
	end_date: Date(),
}

game:
{
	_id: ,
	name: 'a',
	type: 't'
}

team: 
{
	_id: ,
	name: 'b',
	founded: 1991,
	location: 'a'
}