@Override
    public boolean equals(Object other) {
        if (other == this) return true;
        if ( ! (other instanceof SubstituteString)) return false;
        return this.stringValue.equals(((SubstituteString)other).stringValue);
    }
Perform the substitution in this, by looking up in the given properties,
and returns the resulting string

@param context the content which is used to resolve profile variants when looking up substitution values
@param substitution the properties in which values to be substituted are looked up
container-search/src/main/java/com/yahoo/search/query/profile/SubstituteString.java