MHV-63085: Added api endpoint for getting a user's treatment facilities

[mattwrightva]

Summary

• Added an API endpoint to get a user's treatment facilities for the account summary portion of the Blue Button report
• Because we don't need data about the user's preferred treatment facilities we can just use the get patient MHV endpoint for this

Related issue(s)

https://jira.devops.va.gov/browse/MHV-63085

Implement Download all-Account Summary information

Description
Implement Download all-Account Summary information

NOTE: This story is for getting information from MHV into vets-api

Testing done

A test was added for the new client method

Screenshots

No UI changes

What areas of the site does it impact?

MHV medical records

Acceptance criteria

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No error nor warning in the console.
• Events are being sent to the appropriate logging solution
• Documentation has been updated (link to documentation)
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Feature/bug has a monitor built into Datadog (if applicable)
• If app impacted requires authentication, did you login to a local build and verify all authenticated routes work as expected
• I added a screenshot of the developed feature

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?