Enforce use of govuk_link_to et al

[paulrobertlloyd]

Context

Add custom cops to check for use of govuk_link_to and govuk_button_to helpers. Also added a cop to check for use of govuk_submit, but disabled until all forms are using the form builder.

This follows a similar PR to that on Apply.

Changes proposed in this pull request

• Add custom cops
• Fix instances of helpers not being used
• Fix a type (missing space in allocations copy)

Guidance to review

Checklist

• Make sure all information from the Trello card is in here
• Attach to Trello card
• Rebased master
• Cleaned commit history
• Tested by running locally
• Product Review

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[defong]

Should this be a gem thingy now? I think Register also has a clone

[paulrobertlloyd]

@defong I wondered if the constituent gems should provide cops somehow – see this issue on the form builder repo. Same thing could possibly be said of the components gem. @peteryates

[peteryates]

These look great 🙌🏽 Nice work.

I'd be more than happy for a set of cops to be distributed with both the form builder and components gems. There are still a few gotchas that I see (i.e., having to specify link_errors on the first checkbox/radio in a fieldset 🤦🏽) that they'd definitely help with.