@Nullable
    @Override
    public Boolean isResponseStreaming(Type resultType, @Nullable MediaType contentType) {
        if (contentType != null && contentType.is(MediaType.ANY_TEXT_TYPE)) {
            return false;
        }
        final Class<?> clazz = typeToClass(unwrapUnaryAsyncType(resultType));
        if (clazz == null) {
            return null;
        }

        if (CharSequence.class.isAssignableFrom(clazz)) {
            return false;
        }

        return null;
    }
A {@link ResponseConverterFunction} which creates an {@link HttpResponse} when:
<ul>
  <li>the {@code result} is an instance of {@link CharSequence}</li>
  <li>the {@code "content-type"} of the {@link ResponseHeaders} is {@link MediaType#ANY_TEXT_TYPE}</li>
</ul>
Note that this {@link ResponseConverterFunction} is applied to an annotated service by default,
so you don't have to specify this converter explicitly.
core/src/main/java/com/linecorp/armeria/server/annotation/StringResponseConverterFunction.java