Setup Oauth and devise authentication

<p><strong>Q: What was the request about? </strong><br>Set up <span style="color:rgb(95, 99, 102); font-family:lato,sans-serif">a Rails application with&nbsp;</span>Twitter OAuth and Devise.<br><br><strong>Q: How did you help with the request?</strong><br>We installed the required gems, added the required configuration, and troubleshooted the interaction with Twitter.<br><br><strong>Q: Any best practices &amp; key learnings you can share?</strong></p><p>- Configure OAuth in one place only (not both in devise.rb and omniauth.rb)</p><p>- Make sure you are using&nbsp;the actual&nbsp;consumer secret and token, NOT the API keys to set up omniauth</p><p>- The error message invalid_credentials covers a wide variety of possible mistakes</p>