Provide a way to say that an authority doesn't have a homepage

[hsenag]

At present if you leave the "Home page" link blank, then alaveteli guesses a URL based on the email domain. For small authorities without their own domain this is usually wrong, e.g. https://www.whatdotheyknow.com/body/clifford_road_primary_school_ipswich currently links to http://www.hotmail.co.uk

We could put something invalid instead but it'd be better to have an explicit value to disable the link completely. On the other hand I don't remember ever getting a support request from a user confused by it, so it's probably low priority.

[garethrees]

Related to #6434 which covers the calculated homepage problem, but we should also have a way of saying no homepage.

[garethrees]

Might be resolved by a better implementation of #6434 (comment)

• nil – missing homepage
• empty string – no homepage
• calculated homepage only generated for default form value if one doesn't exist

[RichardTaylor]

+1

When listing Local Family Justice Boards many of the contact email addresses don't have domains corresponding to websites for the boards, and many of the boards don't have a home page to link to.

https://www.whatdotheyknow.com/body/list/lfjb

Had I been able to add a special tag eg .no_calculated_homepage to prevent home pages being calculated I'd have done so in many cases.