move to openapi json definitions

[tylanderson]

Moves OpenAPI definitions from YAML to JSON format. Originally reported in Element84/earth-search#61. While it looks like the spec is fine with this being served as YAML, in order to conform more with OCG Features it seems to make sense to switch.

Proposed Changes:

1. Add OpenAPI JSON conversion from YAML
2. Serve OpenAPI JSON document instead of YAML

PR Checklist:

• I have added my changes to the CHANGELOG or a CHANGELOG entry is not required.