Incorrect / misleading error information provided when validating request body

[markgreenwood]

Version: 5.10.6

Scenario:

• The OpenAPI spec denotes a requestBody with multiple composite "datum" fields that have a common Datum schema also defined in the OpenAPI spec (there are three of these in my example).
• The Datum schema has fields value (of type number) and unit (of type enum defined in the OpenAPI spec).
• The example repo for this is here: https://github.com/markgreenwood/openapi-backend-validation-bug

Expected behavior:

• A composite field that fails to validate should report an error with instancePath and schemaPath that both reflect that field's identity (i.e. contain the name of the invalid field).
• If multiple fields fail validation, there should be multiple errors that each contain the information described above.

Actual behavior:

• If any fields using the Datum schema OTHER than the first one in the spec are provided non-numeric values, the error's schemaPath reports validation failure with the name of the FIRST field listed that uses the Datum schema, not the one that actually failed validation. (In the example, if weightis provided a non-numeric value, the schemaPath incorrectly reports distance as the culprit that failed validation.)
• If multiple fields fail validation, the errors array only contains one error, not all the ones that failed to validate. (In one of the example tests, both weight and temperature are provided non-numeric values, but only one error is reported and its schemaPath incorrectly reports distance as being invalid.)

Steps to reproduce:

• Clone or fork the example repo, install dependencies with npm ci, and then run api.test.ts using npm run test. Two of the tests describing the expected behavior above should fail.