Ideas for openapi.yaml improvements (part 2)

[KellyStathis]

• incorporate robust example responses and request bodies - we only have two for a DOI and they are incomplete
• add more response codes, especially error codes
• the report structure for creating a report wasn't accurate and is probably still not accurate; we could update this to support users in providing usage reports
• for requests with a "query" parameter other than DOIs (clients, providers, events), explain what is searchable