Laktory

Fixed
* Accessing custom DataFrame functions in custom namespace in SparkChainNode execution

Added
* Support for Polars with FileDataSource
* Support for Polars with FileDataSink
* Support for PolarsChain transformer
* Polars DataFrame extension
* Polars Expressions extension
Breaking changes
* Refactored column creation inside a transformer node
* Moved laktory Spark dataframe custom functions under a laktory namespace.

Added
* Support for SQL expression in SparkChain node
* Limit option to Data Sources
* Sample option to Data Sources
* Display method for Spark DataFrames
Updated
* Stack model environments to support overwrite of individual list element
Fixed
* Pipeline Node data source read with DLT in debug mode

Updated
* Install instructions
Breaking changes
* Re-organized optional dependencies
* Remove support for Pulumi python

Fixed
* Updated ReadMe
* Stack Validator unit test

Added
* `Pipeline` model, the new central component for building ETL pipelines
* `PipelineNode` model, the `Pipeline` sub-component defining each dataframe in a pipeline
* `FileDataSink` and `TableDataSink` sinks models
* `PipelineNodeDataSource` and `MemoryDataSource` sources model
* Future support for Polars and other types of dataframe
Updated
* Enabled CDC support for both `FileDataSource` and `TableDataSource`
Breaking changes
* Merged `DataEventHeader` into `DataEvent` model
* Renamed `EventDataSource` model to `FileDataSource`
* Renamed `name` attribute to `table_name` in `TableDataSource` model
* Removed `SparkChain` support in DataSources
* Renamed `Pipeline` model to `DLTPipeline` model
* Cloud resources moved under models.resources.{provider}.{resource_class} to avoid collisions with future classes.
* Removed `TableBuilder`. `PipelineNode` should be used instead