Refactor skip controller

[thomasiles]

Small refactor of passing values to the skip controller views

Replace template locals with a single instance variable.

• Remove back_link from skip controller
• Remove template local from skip_controller
• Add view tests for secondary_skip#edit

Trello card:

Things to consider when reviewing

• Ensure that you consider the wider context.
• Does it work when run on your machine?
• Is it clear what the code is doing?
• Do the commit messages explain why the changes were made?
• Are there all the unit tests needed?
• Has all relevant documentation been updated?

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
59.7% Duplication on New Code

See analysis details on SonarQube Cloud