[KM-437][DB] add mysql, sqlserver, bigquery, snowflake connections

[NOTICKET][DB] pisahin db credential ke folder model. add ingestion endpoint at db_client to use db pipeline. add router db_client di main.

edit document for new pipeline

update document

[NOTICKET]: add document pipeline, simplify document API

[NOTICKET] Init db_client endpoint

[KM-467] [DED][AI] Orchestration Agent - Init