This pull request adds 3 functions (and corresponding tests):
`testhelpers/response_validation.go`:
- `ValidateResponse`
- `ValidateResponseData`
field_data.go:
- `ValidateStrict` (has the "strict" validation logic)
The functions are primarily meant to be used in tests to ensure that the responses are consistent with the defined response schema. An example of how the functions can be used in tests can be found in #18636.
### Background
This PR is part of the ongoing work to add structured responses in Vault OpenAPI (VLT-234)
Anton Averchenkov