RFC spec states Http headers are case-insensitive:
Are HTTP headers case-sensitive?
In our source code we set headers in [org.apache.hc.core5.http.HttpMessage](https://github.com/apache/httpcomponents-core/blob/master/httpcore5/src/main/java/org/apache/hc/core5/http/HttpMessage.java) implementations but the the APIs do not specify that the headers are matched with case-insensitivity. For example in HttpClient V3 the contract specifies it's case-insensitive. Can anyone help me figure out whether the HttpMessage interface is case-insensitive or not?
I've tried looking for answers in javadoc and other SO Q&A posts.