Autogenerated operation_id

[AnotherOneAckap]

Hi there! Thank you for the great piece of code you've done.

I am often working with vendor provided API specification, which have some issues.
Unfortunately these specs are too big and updates frequently to fix them manually.
One of the most often issues I met was missing operationId, which is not required as of OpenAPI spec 3.0.1

Now OpenAPI::Client just silently skips such operations, I propose to autogenerate some operationId in this case.
Tried to make them readable:

1. Take first verb from method
2. Remove {params} from path
3. Convert all slashes and dashes to underscore