[Code chat] Create connection and activate indexing

This issue is to enable the embedding pipeline on gitlab production and staging.

• Introduce logging
• Change the values in the initializer to true
• Create a connection record on staging to connect to the staging Elasticsearch cluster
• Create a connection record on production to connect to the production Elasticsearch cluster
• Monitor the migration worker logs and elasticsearch logs
• Verify that the code index was created succesfully

[Connection record] One-click connect to Advanc... (#525344 - closed) will make it easier to create the connection records. It's up to the engineer to choose to implement that first or create the record via rails console in a CR.