Support for PostgreSQL hstore

[techteam-bln]

Describe the Feature Request

Support the map like PostgreSQL HStore feature in the SQL feature provider as result type.

Describe the Use Case

While working with OSM data, you can have tag column, with all availabe tags on the features.
As company internal dataprovider, i doesn't know, what tags are interesting for different users and base on the big variety of tags it is not usefull to generate a new cloumn for every tag.
If all tags would be automatic generated into a property , our users can filter this information's in later processes.

Describe Preferred Solution

It would be nice to have a new resultype like "VALUE_MAP"

myTagProperty:
        sourcePath: my_tags
        type: VALUE_MAP
        valueType: STRING

results in:

{
  "type" : "Feature",
  "id" : "1",
  "geometry" : {
    "type" : "Point",
    "coordinates" : [ 7.0, 50.0 ]
  },
  "properties" : {
    "name" : "Beispiel",
    "inspireId" : "https://example.org/id/soziales/kindergarten/1",
    "tags" : {
      "type" : "Kinderbetreuung",
      "href" : "https://inspire.ec.europa.eu/codelist/ServiceTypeValue/childCareService"
      "thoroughfare" : "Beispielstr.",
      "locatorDesignator" : "123",
      "postCode" : "99999",
       "adminUnit" : "Irgendwo"
      "telephoneVoice" : "0211 16021740",
      "typeOfOccupant" : "vorschule",
      "numberOfOccupants" : 20
    } 
  }
}

Additional Information

A additional enhancement would be to queryalbe the hstore columns.