@Override
    public boolean equals(Object o) {
        return o instanceof ConfigCacheKey && key.equals(((ConfigCacheKey) o).getKey())
                && defMd5.equals(((ConfigCacheKey)o).defMd5);
    }
Constructs new key

@param name           config definition name
@param configIdString Can be null.
@param namespace      namespace for this config definition
@param defMd5         MD5 checksum of the config definition. Never null.
config/src/main/java/com/yahoo/vespa/config/ConfigCacheKey.java