Support for deriving property names from DynamoDBContext attributes

[danielmarbach]

Describe the feature.

When using the DynamoDB context users can attribute their classes with attributes like DynamoDBHashKey, DynamoDBRangeKey and DynamoDBProperty. These attributes allow overriding the property name. Currently when the mapper is used with classes containing those attributes all renamed property need to redundantly declare JsonPropertyName to make the mapper respect the proper names.

    class Customer
    {
        [DynamoDBHashKey("PK")]
        [JsonPropertyName("PK")]
        public string PartitionKey { get; set; }

        [DynamoDBRangeKey("SK")]
        [JsonPropertyName("SK")]
        public string SortKey { get; set; }

        [DynamoDBProperty("customer_preferred")]
        [JsonPropertyName("customer_preferred")]
        public bool CustomerPreferred { get; set; }
    }

With .NET 7 and higher it is possible to add IJsonTypeInfoResolver implementations that get access to either reflection based or source generation based metadata. With that in place it is possible to extract the property information, check for the attributes and emit corresponding property names automatically which would make it possible to use a class without having to attribute properties. Example

    class Customer
    {
        [DynamoDBHashKey("PK")]
        public string PartitionKey { get; set; }

        [DynamoDBRangeKey("SK")]
        public string SortKey { get; set; }

        [DynamoDBProperty("customer_preferred")]
        public bool CustomerPreferred { get; set; }
    }

Additional Context

Pseudo code (just a brainstorm, there might be more elegant solutions)

public class DynamoDBContextAwareTypeInfoResolver: DefaultJsonTypeInfoResolver
{
    public override JsonTypeInfo GetTypeInfo(Type type, JsonSerializerOptions options)
    {
        JsonTypeInfo typeInfo = base.GetTypeInfo(type, options);
        if (typeInfo.Kind == JsonTypeInfoKind.Object)
        {
            foreach (JsonPropertyInfo property in typeInfo.Properties)
            {
                var attribute = property.AttributeProvider.GetCustomAttributes(typeof(DynamoDBRenamableAttribute));
                if(attribute is DynamoDBRenamableAttribute renameAttribute) {
                    property.Name = renameAttribute.AttributeName;
                }
            }
        }
        return typeInfo;
    }
}
``