feat(backend): Add welcome message

src/Service/UserService.php

@@ -64,6 +64,36 @@ public function getOrCreateUser(string $slackUserId): ?User
  ],
  ]);
 
- return $this->Users->saveOrFail($user);
+ $user = $this->Users->saveOrFail($user);
+
+ $this->sendWelcomeNotification($user);
+
+ return $user;
+ }
+
+ /**
+ * @param \App\Model\Entity\User $user The user.
+ * @return void
+ */
+ protected function sendWelcomeNotification(User $user): void
+ {
+ $welcomeMessage = 'Hello there 👋' . PHP_EOL;
+ $welcomeMessage .= PHP_EOL;
+ $welcomeMessage .= '*Welcome to GibPotato!*' . PHP_EOL;
+ $welcomeMessage .= PHP_EOL;
+ $welcomeMessage .= ' - Every day, you get five 🥔' . PHP_EOL;
+ $welcomeMessage .= ' - You can gib them to people as a token of appreciation.'
+ . 'Simply @ mention them and add a 🥔 to your message.' . PHP_EOL;
+ $welcomeMessage .= ' - Alternatively, you can also react to a message with a 🥔. '
+ . 'They either go to the people mentioned in the message or, '
+ - 'if nobody was mentioned, to the author of the message.' . PHP_EOL;
+ $welcomeMessage .= PHP_EOL;
+ $welcomeMessage .= 'Hope you\'ll enjoy using GibPotato. '
+ . 'Make sure to join <#' . env('POTATO_CHANNEL') . '> as well.';
+
+ $this->slackClient->postMessage(
+ channel: $user->slack_user_id,
+ text: $welcomeMessage,
+ );
  }
 }