Add a CRUD template to the templates

[burbas]

I think it would be a lot more intuitive to understand and use nova if it could come with a template with the basic CRUD operations over a given domain model , so that the user could see how can he define the different exposed methods using either querystring or json.
Ideally the template could also contain the code to decode (using a serializer) and fetch some fields of the json
and also the code in order to encode back and send the json response.

The template could include a controller with the methods

• GET (querystring , responds in json)
• POST (receives json , responds in json)
• PUT (receives json , responds in json)
• DELETE (receives query string , responds with status or whatever)

-module(pet_controller).
-export([get/1, create/1, delete/1,update/1]).

get(Req=#{bindings := #{<<"id">> := Id}})->
   .....
   Pet= fetch_pet_from_somewhere(Id),
   Encode= thoas:encode(Pet),
   {json,200,#{},Encode}.

get(Req=#{parsed_qs:= #{<<"id">> := Id}})->
   .....
   Pet= fetch_pet_from_somewhere(Id),
   Encode= thoas:encode(Pet),
   {json,200,#{},Encode}.

create(Req=#{json := { <<"id">> := Id , <<"hair_color">> := HairColor } })->
    insert_to_db(Req),
     {json,200,#{},<<"created">>}.

update(Req=#{json := { <<"id">> := Id , <<"hair_color">> := HairColor } })->
    update_to_db(Req),
     {json,200,#{},<<"updated">>}.

delete(Req=#{parsed_qs:= { <<"id">> := Id } })->
    delete(Req),
     {json,200,#{},<<"deleted">>}.  
 

The datalayer could just be a mock or another module with undefined methods or just some constant in the method , it doesn't rlly matter but the important part is for the new user to see how he handles json/binding/querystring, serialization,deserialization , json deconstruction (fetching particular fields)

And ideally this template could just be started and checked out with swagger.

P.S The idea came from C# where there are a couple of web api templates pic related

Originally posted by @sanzor in novaframework/nova#217