Add native support for OpenSearch in Preset via opensearch-dbapi connector

What is the problem or goal the end user is trying to solve or accomplish?

Users want to connect OpenSearch clusters (e.g., from Aiven or AWS) to Preset using the SQL API, in order to query data and build dashboards. While OpenSearch is widely used as a fully open-source alternative to Elasticsearch, it is not currently supported by Preset out-of-the-box.

How are they solving it currently?

Some users attempt to use the "Elasticsearch (SQL API)" connector in Preset, but this fails because OpenSearch exposes its SQL plugin at / _plugins/_sql, whereas the connector expects /_sql. This leads to a 405 Method Not Allowed error.

What is the recommended solution by the Customer?

Support OpenSearch as a first-class connector by optionally integrating the opensearch-dbapi dialect, which is built specifically for OpenSearch SQL and supports the correct API endpoints (/_plugins/_sql). This would allow Preset to support both OpenSearch and Elasticsearch without breaking compatibility.