private void updateEndpoint(@Nullable Endpoint endpoint) {
        this.endpoint = endpoint;
        autoFillSchemeAuthorityAndOrigin();
    }
Creates a new instance. Note that {@link #init()} method must be invoked to finish
the construction of this context.

@param sessionProtocol the {@link SessionProtocol} of the invocation
@param id the {@link RequestId} that contains the identifier of the current {@link Request}
          and {@link Response} pair.
@param req the {@link HttpRequest} associated with this context
@param rpcReq the {@link RpcRequest} associated with this context
@param requestStartTimeNanos {@link System#nanoTime()} value when the request started.
@param requestStartTimeMicros the number of microseconds since the epoch,
                              e.g. {@code System.currentTimeMillis() * 1000}.
core/src/main/java/com/linecorp/armeria/internal/client/DefaultClientRequestContext.java