Better handling of invalid URLs in link editor

The link editor requires users to enter proper URLs. That means that the URL must start with a protocol like https://. This is rather technical knowledge and users might expect something like www.example.org to work even though it technically must be https://www.example.org.

Options for handling this may be:

1. Automatically adding https:// if the protocol is missing. This might be ok because most sites support TLS.
2. Displaying an error message that a protocol is missing.

Right now the field is just colored in red and doesn’t give any explanation why it is considered invalid. It also does not persist the value likely causing data loss in some situations.

changed milestone to %1.0-alpha6 — Wondrous Whale

added bug label

assigned to @kmohrf

added Cycle [1/25] P3 labels

added To Do label

added moveable label

added Doing label and removed To Do label

mentioned in commit feee41f3

added ready-for-testing label and removed Doing label

removed moveable label

closed

removed ready-for-testing label