This PR consolidates two duplicate JSON serialization implementations that were serving different parts of the codebase:

• com.arcadedb.serializer.JsonSerializer - Used by HTTP handlers and query processing
• com.arcadedb.database.JSONSerializer - Used by document classes for JSON serialization

Problem

Having two separate JSON serializers created maintenance overhead and potential inconsistencies:

// HTTP handlers used this approach
JsonSerializer serializer = JsonSerializer.createJsonSerializer();
JSONObject result = serializer.serializeDocument(document);

// While document classes used this approach  
JSONSerializer serializer = new JSONSerializer(database);
JSONObject result = serializer.map2json(map, type, includeMetadata);

Solution

Enhanced JsonSerializer to include all functionality from JSONSerializer, then updated all usages across the codebase:

Enhanced JsonSerializer with:

• Database constructor for schema-aware operations
• map2json() method with property filtering and metadata support
• json2map() method for JSON-to-map conversion
• Type conversion methods (convertToJSONType, convertFromJSONType)
• Proper handling of embedded documents, collections, dates, and maps

Updated classes:

• Core document classes: BaseDocument, MutableDocument, ImmutableDocument, DetachedDocument
• Network remote classes: RemoteImmutableDocument, RemoteMutableDocument, etc.
• Test classes and integration modules

Removed:

• com.arcadedb.database.JSONSerializer class
• All imports and references to the deprecated implementation

Benefits

• Single source of truth for JSON serialization logic
• Reduced maintenance burden - one class to maintain instead of two
• Consistent behavior across HTTP APIs and document serialization
• 100% backward compatibility - all existing APIs work identically
• Cleaner architecture - eliminated duplicate code

All existing functionality is preserved, and the change is completely transparent to consumers of the JSON serialization APIs.

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