https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/bind/annotation/RequestHeader.html

2019
https://www.baeldung.com/spring-rest-http-headers

samples
@RequestHeader HttpHeaders
@RequestHeader Map<String, String> headers,
@RequestHeader(value = "optional-header", required = false) String optionalHeader) 
@RequestHeader(value = "optional-header", defaultValue = "3600") int optionalHeader)