Warn users when redirection happens

[jesmrec]

This comes from: https://github.com/owncloud/android/pull/3074#issuecomment-789682250

If a redirection happens, user must be notified and approve explicitly the issue (a similar way to do as in a self-signed certificate)

iOS example:

AC:

• When the URL is checked, if a redirection happens, a dialog/alert/whatever is displayed to notify the issue
• When the user accepts, auth flow goes on
• In case the user does not accept the redirection, the auth flow stops

NOTE: this is the same way to do as in a self-signed/not secured server certificate

TASKS

• [ ] Research (if needed)
• [ ] Create branch feature/feature_name
• [ ] Development tasks
  • [ ] Create new exception when redirection 301 or 302 happens
  • [ ] ...
• [ ] Code review and apply changes requested
• [ ] Design test plan
• [ ] QA
• [ ] Merge branch feature/feature_name into master

PR

• App
• Library (if needed)