-- host_applications: direct association between a host and an application.
-- Allows explicitly tagging a host with an application regardless of ports.
-- One application can only be linked once to a given host.
CREATE TABLE IF NOT EXISTS host_applications (
    host_id        BIGINT NOT NULL REFERENCES hosts(id)        ON DELETE CASCADE,
    application_id BIGINT NOT NULL REFERENCES applications(id) ON DELETE CASCADE,
    PRIMARY KEY (host_id, application_id)
);