Provide detailed reference documentation for the new endpoint infrastructure

[wilkinsona]

Some things to document:

• @Endpoint
• @JmxEndpointExtension
• @ReadOperation
• @Selector
• @WebEndpointExtension
• WebEndpointResponse
• @WriteOperation
• Type conversion
• Web request predicates (GET for read, POST for write, produces, consumes, etc)
• Default response status for web operations (200, 404 for null with GET, 204 for null with POST, etc)
• Support for HTTP range requests to operations that return a Resource (WebFlux and Spring MVC only)
• -parameters is required to infer parameter names
• @Nullable for optional parameters

[shabino]

Please consider documenting endpoints.<endpoint name>.cache.time-to-live and that the value is expressed in millis.

[shabino]

See #11010 for a suggestion regarding @Selector parameter naming.

[snicoll]

Please consider documenting endpoints..cache.time-to-live and that the value is expressed in millis.

It is already documented. Also, your IDE should tell you that when you use that key in application.properties/yml

[philwebb]

We should add a small section in the reference docs to explain what the cache is for and how to configure it.

[snicoll]

There's a bunch of stuff already done as part of #10176. I'll review what's missing still.

[snicoll]

Also, let's make sure we document the dependency to -parameters (see #11010 (comment))

[manderson23]

In the documentation regarding unauthenticated access to actuator with the sample code you provide would it be useful to mention that csrf being enabled by default results in calls to POST end points being forbidden? This caught be out on upgrade from 1.5.x.

[snicoll]

@manderson23 see #11758 (this issue isn't supposed to touch that area anyway).