Major Description
To make it easy to use/modify the semantic annotation, we want to have a shorter API to update the metadata in a dataframe.
Currently we have
df.withColumn("col1", col("col1").alias("col1", metadata=metadata))
to update the metadata without changing the column name, and this is too verbose. We want to have a syntax suger API
df.withMetadata("col1", metadata=metadata)
to achieve the same functionality.
A bit of background for the frequency of the metadata update: We are working on inferring the semantic data types and use them in AutoML and store the semantic annotation in the metadata. So in many cases, we will suggest the user update the metadata to correct the wrong inference or manually add the annotation for weak inference.
