Allow re-writes to metadata JSON files

[npatki]

Problem Description

Currently, the metadata.save_to_json function is meant to throw an error if you provide a filename that already exists. We did this so that users wouldn't accidentally overwrite existing metadata files.

However, this become an issue if you want to read from a file, update the metadata (to correct it), and then write it back to the same file.

from sdv.metadata import Metadata

metadata = Metadata.load_from_json(filepath='metadata.json')
metadata.update_column(
    table_name='guests',
    column_name='guest_email',
    sdtype='email')
metadata.save_to_json(filepath='metadata.json')

ValueError: A file named 'metadata.json' already exists in this folder. Please specify a different filename.

Expected behavior

Allow users a parameter that bypasses this check. It should be off by default (maintaining status quo), but users could always toggle it to allow re-saving to the same file.

To keep consistency with AI connectors, we can call this parameter mode. Possible values are:

• (default) 'write': The status quo. AKA write the metadata into a new file, and raise an error if the file already exists.
• 'overwite': Write the metadata into the file. If it already exists, re-write the file

metadata.save_to_json(
  filepath='metadata.json',
  mode='overwrite'
)