add and integrate with Spring / Grails security for the client / server

[nathandunn]

Requirements:

• consistent error handling (codes) and JSON return if more information needed
• . . . .

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• Can swagger provide authentication layer?
• How does user information get loaded?

use OAuth2 . . . in resources.groovy

https://swagger.io/docs/specification/authentication/oauth2/

https://swagger.io/docs/specification/authentication/ . . . with an ApiKey . . or others

• multiple authentication schemas: https://github.com/swagger-api/swagger-ui/issues/2399
• authentication: https://bluesliverx.github.io/grails-spring-security-oauth2-provider/v3/manual/guide/gettingStarted.html#createDomainClasses

[nathandunn]

• https://developer.okta.com/blog/2018/04/19/okta-with-grails

• https://grails-plugins.github.io/grails-spring-security-oauth2-provider/latest/manual/guide/gettingStarted.html#resourceAccess