Improve specification of examples in the Register Your Data API to conform properly with OpenAPI spec

**Brief Description**
The Register Your Data API includes example responses in a way that does not match the OpenAPI specification.  This was discussed in PR https://github.com/IATI/iati-unified-platform-docs/pull/3.

**Severity**
Low

**Action**
To close this issue the examples should be refactored in the YAML specification.