Allow domains to belong to multiple third parties

Change the unique constraint on common_third_party_domains from (domain)
to (common_third_party_id, domain) so a domain like google.com can be
associated with Google, Google Analytics, Google AdSense, etc.

Also fix Beamer domain (was hotjar.com, now getbeamer.com) and preserve
the original url.Parse error in pgconn DSN parsing.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/proboctl/pgconn/pgconn.go

@@ -25,7 +25,7 @@ import (
 func NewPgClientFromDSN(dsn string) (*pg.Client, error) {
 	u, err := url.Parse(dsn)
 	if err != nil {
-		return nil, fmt.Errorf("cannot parse DSN (check URL format)")
+		return nil, fmt.Errorf("cannot parse DSN: %w", err)
 	}
 
 	var opts []pg.Option