generate OpenAPI specs openapi.json

[Jean-Baptiste-Lasselle]

With Loopback we have supported tools for that : https://www.npmjs.com/package/@loopback/openapi-v3

Also, I want to add one more REST Endpoint, and make that one at least, a GRaphQL endpoint see https://www.npmjs.com/package/openapi-to-graphql

I will also validate by re-generating the source code of the REST API endpoints, using tols like :

• https://github.com/OpenAPITools/openapi-generator
• https://openapi-generator.tech/#try