Footer layout isn't aligned with content layout

[dashouse]

As noticed on GovWifi, the flexbox auto layout used in the footer means that the columns do not lock into the grid.

Example from GovWifi

With equal content, the content is not distributed evenly, the first column takes up more space. Adding content to the second or third column will take away space from the first, which is why the GovWifi example looks almost right, but it's coincidental.

Recreated in the Prototype Kit

Is there anything we can add to the flexbox properties to ensure min or max width of content?

## Done when

• TBC
• "Details of breaking change" section below completed to help with writing release notes

Details of breaking change

• which users are affected: TBC
• the change that’s been made: TBC
• changes users will have to make: TBC
• impact of users not making those changes: TBC

[NickColley]

I've had a look into this, I think the way flexbox works means that even though the proportions are correct in certain scenarios the footer will not align with the main grid system.

I have proposed a fix to improve the specific issues raised by Dave here for three columns: #1542

I believe to fix this we need to improve how the footer works:
https://github.com/alphagov/govuk-frontend/tree/spike-only-default-two-thirds-footer-for-two-sections

This will require a small but breaking change, so will put this against the 4.0.0 milestone

[36degrees]

We may want to look at #1284 at the same time as this.

[vanitabarrett]

As discussed in v4 prioritisation, we think this work is important but it's quite broad at the moment. We should probably do a timeboxed investigation into this issue and this related one to explore a few different layout systems for the footer and see how they perform.

We should keep in mind these other issues with the footer, some of which may be fixed by switching to a new layout system.