improve variable serialization for arrays and hashes (#40)

- Add proper serialization support for Array and Hash variable types
- Fix serialization for integers and booleans
- Maintain existing string serialization behavior

This change ensures that arrays, hashes, integers, and booleans are 
properly serialized when making queries with variables to the query api.

Author: rcmoret

lib/sanity/http/where.rb

@@ -41,7 +41,7 @@ def query_and_variables
         else
           {}.tap do |hash|
             variables.each do |key, value|
-              hash["$#{key}"] = "\"#{value}\""
+              hash["$#{key}"] = serialize_variable_value(value)
             end
           end
         end.merge(query: groq_query)
@@ -56,6 +56,17 @@ def request_body
 
         query_and_variables.to_json
       end
+
+      def serialize_variable_value(value)
+        case value
+        when String
+          "\"#{value}\""
+        when Array, Hash
+          value.to_json
+        else
+          value.to_s
+        end
+      end
     end
   end
 end