Replace swagger-request-validator with openapi4j for xml validation functionality
- Update spec with xml request schema
- Refactor pom: organize/add comments, add openapi4j, remove swagger-request-validator, add dependencies for tests
- Replace validator with openapi4j parser, validator, and converting xml to a JsonNode
- Reorganize tests, add xml tests, add assertJ validation for post requests to further assert that the correct exception occurred
Replace swagger-request-validator with openapi4j for xml validation functionality