HEEDLS-865 Add endpoint with json centres data for find your centre map

[AlexJacksonDS]

JIRA link

https://softwiretech.atlassian.net/browse/HEEDLS-865

Description

Added an endpoint that returns JSON data for centres to display on the Find Your Centre map

Screenshots

N/A

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.

[livzorn]

Nice work! Just left one small note

[DanBloxham-sw]

Couple of minor points plus Olivia's comments, but otherwise looks good.

[DanBloxham-sw]

Looks good.