HEEDLS-531 - replaced all error redirects with StatusCodeResults

[DanBloxham-sw]

JIRA link

https://softwiretech.atlassian.net/browse/HEEDLS-531

Description

Replaced any Redirects to the LearningSolutions Error page to be a StatusCodeResult(500). Looking through the individual cases, they all seemed to be random errors that occurred rather than forbidden or not found pages, so I only used StatusCodeResult(500)

Screenshots

N/A

Developer checks

I have:

• Run the formatter and made sure there are no IDE errors.
• Written tests for the changes (controller, data services, services, view models etc) and manually tested my work with and without JavaScript. Full manual testing guidelines can be found here: https://softwiretech.atlassian.net/wiki/spaces/HEE/pages/6703648740/Testing
• Updated/added documentation in Swiki and/or Readme.
• Updated my Jira ticket with information about other parts of the system that were touched as part of the MR and have to be sanity tested to ensure nothing’s broken.
• Scanned over my own MR to ensure everything is as expected.

[stellake]

Looks good! 👍