RDS-478: Add auto detection for time column in dgan MIF.

* Add dgan auto config class and logic for time column detection.
* Provide access to `ModelLogger` in the `ConfigUpdater` class, so messages can be logged during processing.
* Use str enums for dgan configs to work with `json.dumps`

GitOrigin-RevId: d3d2f2d3237052337b8064b66d6951348d30b127

src/gretel_synthetics/timeseries_dgan/config.py

@@ -2,26 +2,26 @@
 from enum import Enum
 
 
-class OutputType(Enum):
+class OutputType(str, Enum):
     """Supported variables types.
 
     Determines internal representation of variables and output layers in
     generation network.
     """
 
-    DISCRETE = 0
-    CONTINUOUS = 1
+    DISCRETE = "discrete"
+    CONTINUOUS = "continuous"
 
 
-class Normalization(Enum):
+class Normalization(str, Enum):
     """Normalization types for continuous variables.
 
     Determines if a sigmoid (ZERO_ONE) or tanh (MINUSONE_ONE) activation is used
     for the output layers in the generation network.
     """
 
-    ZERO_ONE = 0
-    MINUSONE_ONE = 1
+    ZERO_ONE = "zero_one"
+    MINUSONE_ONE = "minusone_one"
 
 
 @dataclass