SupportsStaging (Flink : 2.0-SNAPSHOT API)

```
@PublicEvolving
public interface SupportsStaging
```
Interface for DynamicTableSinks that support atomic semantic for CTAS(CREATE TABLE AS SELECT) or RTAS([CREATE OR] REPLACE TABLE AS SELECT) statement using a two-phase commit protocol. The table sink is responsible for returning a StagedTable to tell the Flink how to implement the atomicity semantics.
If the user turns on TableConfigOptions#TABLE_RTAS_CTAS_ATOMICITY_ENABLED, and the DynamicTableSink implements SupportsStaging, the planner will call method applyStaging(StagingContext) to get the StagedTable returned by the sink, then the StagedTable will be used by Flink to implement a two-phase commit with the actual implementation of the StagedTable.

Nested Class Summary

Nested Classes
Modifier and Type	Interface	Description
`static interface`	`SupportsStaging.StagingContext`	The context is intended to tell DynamicTableSink the type of this operation.
`static class`	`SupportsStaging.StagingPurpose`	The type of operation the staging sink is for.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`StagedTable`	`applyStaging(SupportsStaging.StagingContext context)`	Provides a `SupportsStaging.StagingContext` for the sink modification and return a `StagedTable`.

- Method Detail
  - applyStaging
```
StagedTable applyStaging(SupportsStaging.StagingContext context)
```
    Provides a SupportsStaging.StagingContext for the sink modification and return a StagedTable. The StagedTable provides transaction abstraction to support atomicity for CTAS/RTAS. Flink will call the relevant API of StagedTable when the Job status switches,
    Note: This method will be called at the compile stage.
    
    Parameters:
    
    context - The context for the sink modification
    
    Returns:
    
    StagedTable that will be leveraged by Flink framework to provide atomicity semantics.