Create claim vets-api client/service code

[kjduensing]

Issue Description

Context

The first "real" step in creating a mileage claim is to create the claim to which expenses are attached.

Impact

This facilitates being able to add expenses (now for simple claims, and in the future for complex claims)

Notes

• There's no need to expose an endpoint for this yet, I don't think. Feel free to comment an opposing viewpoint.
• This image (below) shows that I can add an expense item to the claim request body as I'm making the create claim request. ~This might invalidate department-of-veterans-affairs/va.gov-team#92329~[OUTDATED, SEE BELOW], but following up in this slack thread to be sure.

The create claim endpoint no longer accepts an expense item as part of the request body. Per: https://dsva.slack.com/archives/C05UTPZRZFY/p1725640173491679

Endpoint Path

n/a

Response Schema

n/a

Back end tasks

• [ ] Client code written - calls correct endpoint
• [ ] Service code written - transforms/processes response from client
  • [ ] Handle errors
• ~[ ] Controller endpoint written~
• [ ] Config
  • [ ] settings.test.yml updated if needed
  • [ ] settings.local.yml updated if needed
  • [ ] settings.yml updated if needed
  • [ ] infra-manifests updated if needed
  • [ ] dev
  • [ ] staging
  • [ ] prod
• [ ] Tests written
  • [ ] Unit
  • [ ] Happy path
  • [ ] Exhaustive failure paths
  • [ ] Integration
  • [ ] VCR Cassettes
  • [ ] Betamocks registration
• [ ] Mock data
• [ ] Testing
  • [ ] Unit tests pass ~- [ ] QA testing - try to break it in staging~
• [ ] Improve 1 thing about the codebase
• [ ] Swagger docs updated

Acceptance Criteria

• [ ] Backend tasks complete
• [ ] I have tested it exhaustively locally and/or in dev.

[ayush-chak]

Hey team! Please add your planning poker estimate with Zenhub @hinzed1127 @kjduensing @liztownd