Document recommended CORS config in a server environment

[nyurik]

Most Actix-using services provide some user configuration via .yaml files or CLI parameters. CORS is a common feature that would require to be configurable by the end user. Yet, the current CORS crate API is somewhat complex when it comes to translating end-user provided configuration into API calls.

I think it will be of great help for developers to suggest some ways of specifying CORS values via configuration and translating them to API calls. Note that this is different than the dynamic configuration via allowed_origin_fn or similar.

Configuration Examples

Origins

cors-origins: *
cors-origins: example.com
cors-origins: [ example.com, example.org ]

let origins: String = config.cors_origins;
// FIXME: this won't work because it has to handle "*" differently?
Cors::default().allowed_origin(origins);

Methods

cors-methods: *
cors-methods: GET
cors-methods: [ GET, POST ]

// TODO: Rust example

Headers

cors-headers: *
cors-headers: AUTHORIZATION
cors-headers: [ AUTHORIZATION, ACCEPT ]

// TODO: Rust example