update frontend to use POST instead of GET to match backend api for c…

[coope93]

Are you removing, renaming or moving a folder in this PR?

• No, I'm not changing any folders (skip to TeamSites and delete the rest of this section)
• Yes, I'm removing, renaming or moving a folder

If the folder you changed contains a manifest.json, search for its entryName in the content-build registry.json (the entryName there will match).

If an entry for this folder exists in content-build and you are:

1. Deleting a folder:

   1. First search vets-website for all instances of the entryName in your manifest.json and remove them in a separate PR. Look particularly for references in src/applications/static-pages/static-pages-entry.js and src/platform/forms/constants.js. If you do not do this, other applications will break!
      • Add the link to your merged vets-website PR here
   2. Then, Delete the application entry in registry.json and merge that PR before this one
      • Add the link to your merged content-build PR here

2. Renaming or moving a folder: Update the entry in the registry.json, but do not merge it until your vets-website changes here are merged. The content-build PR must be merged immediately after your vets-website change is merged in to avoid CI errors with content-build (and Tugboat).

⚠️ TeamSites ⚠️

Examples of a TeamSite: https://va.gov/health and https://benefits.va.gov/benefits/. This scenario is also referred to as the "injected" header and footer. You can reach out in the #sitewide-public-websites Slack channel for questions.

Did you change site-wide styles, platform utilities or other infrastructure?

• No
• Yes, and I used the proxy-rewrite steps to test the injected header scenario

Summary

• The caregiver facilities endpoint is being changed from a GET to a POST due to security concerns around values being present in urls with a GET request. This PR updates vets-website make the POST call instead of the GET call.
• This PR will not be merged until this PR is merged. Both are behind a flipper toggle, so there will be no Veteran impact if they are out of sync for a short time.
• 1010 Health Apps
• This work is still behind the caregiver_use_facilities_API toggle

Related issue(s)

• [BE] 10-10CG - Facilities: Replace GET with POST to mitigate PII exposure va.gov-team#99567
• vets-api PR

Testing done

• Updated the unit tests and cypress specs for this feature

Screenshots

No UI changes

What areas of the site does it impact?

10-10CG Form

Acceptance criteria

Quality Assurance & Testing

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Linting warnings have been addressed
• Documentation has been updated (link to documentation *if necessary)
• Screenshot of the developed feature is added
• Accessibility testing has been performed

Error Handling

• Browser console contains no warnings or errors.
• Events are being sent to the appropriate logging solution
• Feature/bug has a monitor built into Datadog or Grafana (if applicable)

Authentication

• Did you login to a local build and verify all authenticated routes work as expected with a test user

Requested Feedback

(OPTIONAL) What should the reviewers know in addition to the above. Is there anything specific you wish the reviewer to assist with. Do you have any concerns with this PR, why?