Add handling for action OPEN_LINK

[philprime]

• Extend the DTO with the new action type OPEN_LINK and field link
• Add the button to the message UI
• Implement logic to present the link in a web browser view

[philprime]

We are introducing three targets:

• SYSTEM_BROWSER, should open link in system browser app.
• IN_APP_BROWSER, should open link in a web browser in the app.
• SHARE_SHEET, should open a share dialog to share the link in another app.