HOFF-738: Session timeout warning(sign in required)

[Rhodine-orleans-lindsay]

What?

• Add session timeout warning content for forms that use the save and exit functionality - HOFF-738. This ticket builds on HOFF-737. Users can choose to signed in or sign out and if they sign out the information saved will not be affected. HOFF-737 and HOFF-738 will be published together.
• This is modelled of off the NHS IHS form (which leverages hof) (see code repo here) and the govuk design system backlog issue for timeout warnings (see code repo here)

  Why?

• To comply with accessibility requirements

  How

• Added showSaveAndExit locals to session-timeout-warning.html to set content to be used by save and exit forms. I added more content to then on the pattern as it was quite unclear that being signed out or signing out wouldn't save any input on the current page if it hadn't previously been saved.
• Added default save-and-exit html template
• Set showSaveAndExit locals to true on /dob step in sandbox/index.js for demo purposes.
• Added showSaveAndExit locals to session-timeout-warning.html to set content to be used by save and exit forms
• Added default save-and-exit html template
• Set showSaveAndExit locals to true on /dob step in sandbox/index.js for demo purposes.
• Added save-and-exit.html to sandbox for demo purposes
• Amended sandbox/pages.json to include flag for save and exit content
• Added config to customise save and exit page
• Added relevant tests
• Amended sessionDialog.js so it can pick up configured warning text instead of it being hard coded
• Added baseUrl to exit href to account for services with base urls
• Amended sandbox/pages.json to include flag for save and exit content
• Amended changelog to include save and exit changes and note about potential breaking changes

Testing?

tested locally in sandbox and in services locally and in branch using a beta version

Anything Else? (optional)

• PR for documentation can be found in hof-guide - https://github.com/UKHomeOfficeForms/hof-guide/pull/22/files
• Demo can be tried on the HOF Demo app

Screenshots (optional)

Session timeout warning for a 'save and exit' form

Default save and exit page after user clicks 'Sign out'

Example of customised save and exit page after user clicks 'Sign out'

Check list

• [x] I have reviewed my own pull request for linting issues (e.g. adding new lines)
• [x] I have written tests (if relevant)
• [x] I have created a JIRA number for my branch
• [x] I have created a JIRA number for my commit
• [x] I have followed the chris beams method for my commit https://cbea.ms/git-commit/ here is an example commit
• [x] Ensure drone builds are green especially tests
• [x] I will squash the commits before merging