title: How to implement a user authentication by phone number in telegram bot?
body: <p>I am creating a telegram chat bot written in java in spring boot and need to verify users by their phone numbers. After entering /start command in bot, I want my users automatically to be verified and to send them a message such as "Welcome, dear Customer".</p>
  
  <p>I stored their numbers in my db, but since it is my first experience in bot applications, I do not have any clue about how to achieve it.</p>