public static Set<SessionProtocol> httpValues() {
        return HTTP_VALUES;
    }
Returns an immutable {@link Set} that contains {@link #HTTP}, {@link #H1C} and {@link #H2C}.
Note that it does not contain HTTPS protocols such as {@link #HTTPS}, {@link #H1} and {@link #H2}.

@see #httpsValues()
core/src/main/java/com/linecorp/armeria/common/SessionProtocol.java