Implement join lobby method via PIN code

Send request providing the pinCode parameter.

• Find lobby by pinCode, otherwise return 404
• Check that user is not already joined this lobby
• Check that user is not the creator of this lobby
• Add user to the joinedPlayers and return lobbyId as a response

https://gitlab.pg.innopolis.university/quiz-web-engine/readme/-/blob/main/Quiz%20walkthrough.png