In order to generate swagger spec, e.g. inside apic, we need to load the app. At the moment, all datasources open connection to databases at the start time and if there is any problem, the whole app crashes, even though we only wanted to query metadata.
The proposal is to modify all connectors to correctly implement a lazy connect method and then modify juggler to allow the user to defer initialization of connections until later.

This issue is created to track the implementation and any feedback are welcomed and appreciated!

spike story: #2176