Make Redirects Editable

[davidsword]

Currently to change a URL, the Redirect has to be deleted and then re-added.

The ability to edit a redirect would improve ease of use.

[bdtech]

@davidsword Thinking this through the default behavior should replace/update the existing redirect.

For example, if you used the CLI to "insert-redirect" or "import_from_csv", this would automatically account for any change of destination URL (currently an error would kick out saying it exists already). The UI would also allow editing the URL as well.

Sound good? Are there any additional considerations?

[GaryJones]

May want to take a look at the last two commits from https://github.com/Automattic/WPCOM-Legacy-Redirector/commits/feature/delete-update-bulk-redirects

Also, look at --skip-validation flag.