Validation with e.g. `redocly` fails with 34 errors and 58 warnings

[jorgenosberg]

Types of errors:

• Server url should not have a trailing slash. Rule: no-server-trailing-slash.
• Operation object should contain summary field. Rule: operation-summary.
• Every operation should have security defined on it or on the root level. Rule: security-defined.

Types of warnings:

• Info object should contain license field. Rule: info-license.
• Operation must have at least one 4XX response. Rule: operation-4xx-response.
• Operation object should contain operationId field. Rule: operation-operationId.
• Component: "collectionResponse" is never used. Rule: no-unused-components.
• Required property 'number' is undefined. Rule: no-required-schema-properties-undefined.

This list is not exhaustive, just a list of one occurrence per type of error/warning.

[joachse]

I don't think it would make sense to use every default rule from redocly.

Server URLs individual to every implementor, and should maybe be added and published by this implementor. But the specification we publish here on github could maybe be an empty list, or to an actual working mock server?

As for most of the other I think a fix to clean up would be.

We could also set up some sort of CI pipeline to validate changes in pull requests?