Allow saving a draft connector

[vpipkt]

Currently when creating a source or destination, if the check doesn't pass, the connector is not saved. This makes it difficult to collaborate with others about misconfigurations, because we have to start over each time, and the proposed configuration is only in one user's browser session.

Allow saving a connector as a draft. Connections cannot be made with draft connectors. Users must opt in to draft connectors (similar to connector builder save on test changes failing).

Once check passes, the connector can be saved in a non-draft state.