feat: Add support for dynamic metadata fields in Elasticsearch index creation

[minglu7]

feat: Add support for dynamic metadata fields in Elasticsearch index creation

This commit enhances the flexibility of our Elasticsearch index creation by allowing dynamic metadata fields to be passed as keyword arguments during the initialization.

Key changes:

• Updated the __init__ method to accept metadata_mappings as part of **kwargs, enabling the customization of metadata fields.
• Merged basic metadata fields with user-defined fields to create a more customizable index mapping.
• Modified the _create_index_if_not_exists method to incorporate the merged metadata fields.

Benefits:

• Improved extensibility: Users can now easily add custom metadata fields without modifying the core implementation.
• Enhanced flexibility: The solution accommodates a variety of metadata types, including text, keyword, date, and numeric fields.
• Simplified API: Passing metadata_mappings directly in kwargs keeps the method signatures clean and intuitive.

This change ensures that our Elasticsearch indices can be tailored to specific application requirements while maintaining a straightforward and flexible API.

[minglu7]

@logan-markewich Actually, I didn't think that much about it. At the time, I just thought that the metadata_mappings could be extracted from **kwargs. However, I think setting it as a named parameter is a good idea; it looks more standardized.

[minglu7]

In this example, metadata_mappings doesn't seem to be a commonly used or particularly important parameter. I think it is an optional and less frequently used parameter. Personally, I believe using **kwargs might be more appropriate.

[nerdai]

In this example, metadata_mappings doesn't seem to be a commonly used or particularly important parameter. I think it is an optional and less frequently used parameter. Personally, I believe using **kwargs might be more appropriate.

Thanks @minglu7. I think I have I agree with Logan here. I believe parameters such as es_url and es_cloud_id would be used the same amount of times as metadata_mappings and both are parameter fields for this class.