In this diff we're handling two errors:
1. When invalid characters were used in the link
2. When an already used link was used
Copies are based on https://www.figma.com/file/a1nkbWgbgjRlrOY9LVurTz/Comm-%2F-Desktop-app?node-id=11341%3A284796&mode=dev, but with some changes:
1. Replaced the first chars to the lowercase so that they are consistent e.g. with our login form.
2. Removed a set of invalid chars from `invalid_characters` error message because it is impossible to present a complete set of invalid chars (we only support `[a-zA-Z0-9]`).