feat: Linear OAuth 2.0 (#10851)

Fixes https://linear.app/chatwoot/issue/CW-3417/oauth-20-authentication
We are planning to publish the Chatwoot app in the Linear [integration
list](https://linear.app/docs/integration-directory). While we currently
use token-based authentication, Linear recommends OAuth2 authentication.
This PR implements OAuth2 support.

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

app/javascript/dashboard/i18n/locale/en/integrations.json

@@ -297,6 +297,12 @@
         "TITLE": "Unlink",
         "SUCCESS": "Issue unlinked successfully",
         "ERROR": "There was an error unlinking the issue, please try again"
+      },
+      "DELETE": {
+        "TITLE": "Are you sure you want to delete the integration?",
+        "MESSAGE": "Are you sure you want to delete the integration?",
+        "CONFIRM": "Yes, delete",
+        "CANCEL": "Cancel"
       }
     }
   },