Add initial database setup and user/artist management functionality

api/queries/users.sql

@@ -2,5 +2,8 @@
 -- name: GetUsernameByID :one
 SELECT user_name FROM users WHERE id = $1;
 
--- name: checkUserExistsByEmail :one
-SELECT id FROM users WHERE user_mail = $1;
+-- name: CheckUserExistsByEmail :one
+SELECT id FROM users WHERE user_mail = $1;
+
+-- name: CreateUser :one
+INSERT INTO users (id, user_name, user_mail, password) VALUES ($1, $2, $3, $4) RETURNING id;