add recon modules for self-hosted databases whose http interface is reachable
without credentials: clickhouse runs arbitrary sql because the default user has
an empty password, confirmed here by reading the server version through the
http interface, and the open-source dgraph alpha has no authentication so its
/health endpoint discloses the cluster while /query and /admin read and drop
all data; a clickhouse that requires a password returns 403 and an alpha behind
an authenticating proxy returns 401 and neither is flagged.
Tigah