[Mozilla Enterprise] Help converting a 'POST' search engine plugin to a Policy ?

[James Pearson]

I have an existing search engine XML file that I would like to convert 
to a Policy entry

The search engine uses the 'POST' method, but I can't work out what the 
"PostData" setting should be in the policies.json file

The search engine XML has:

<Url type="text/html" method="POST" template="https://some.server/search">
         <Param name="data[Search][value]" value="{searchTerms}"></Param>
         <Param name="data[Search][hiddenValue]" value=""></Param>
         <Param name="data[Interface][viewMode]" value="list"></Param>
         <Param name="data[layout]" value="search"></Param>
</Url>

Does anyone know how to translate the above into a suitable "PostData" 
string for a policies.json file ?

Thanks

James Pearson