Heedls 681 Add LH SSO Account Linking Endpoint

[wilkinsm]

JIRA link

https://softwiretech.atlassian.net/browse/HEEDLS-681

Description

Add new endpoint that recieves requests from the LH that links the LH accounts to the DLS accounts.
This is part of the overall Learning Hub SSO linking journey.

Screenshots

Desktop standard

Desktop Already Linked

Desktop Invalid resource id

Tablet

Mobile

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Developer checks

(Leave tasks unticked if they haven't been appropriate for your ticket.)

I have:

• Run the formatter and made sure there are no IDE errors.
• Written tests for the changes (accessibility tests, unit tests for controller, data services, services, view models, etc)
• 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. Links (if any) are below:
  • doc_1_here
• 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.

[wilkinsm]

Need to write up about the new Integration Tests!

[JBsoftwire]

Just a couple of things I noticed about the tests.

[JBsoftwire]

Looks good.

[SteveJacksonSoft]

Looked at everything except integration tests so far.

[SteveJacksonSoft]

Cool, think it's just the two already-existing threads to resolve.