feature request: json sink mapper: support json array and object

[rzorzorzo]

Description:
currently the json sink mapper supports only primitive types (string, int, ...)
other data types, such as lists are ignored silently.
pls add support for lists and objects
maybe log a warning for unsupported data types.

thus for example:

select list:collect(..) as listData
insert into OutStream

@sink (type ... @Map('json'))
define OutStream(listData object)

would create something like:
{event:{listData:[{...},...]}

as workaround i am currently converting the list to a string and then in the receiver i then have to parse the string to get the required list.

Affected Siddhi Version:
5.1.0