fix(ldap): add more logs (#8197)

# Which Problems Are Solved

In case the user bind (user password check for LDAP IdP) fails, there's
no information about what went wrong.
This makes it hard to even impossible to find the cause.

# How the Problems Are Solved

Added logging of the error.

# Additional Changes

Additionally added a log in case no single user (none / multiple) are
found.

# Additional Context

- reported internally

internal/idp/providers/ldap/session.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/go-ldap/ldap/v3"
+	"github.com/zitadel/logging"
 	"golang.org/x/text/language"
 
 	"github.com/zitadel/zitadel/internal/domain"
@@ -172,12 +173,14 @@ func trySearchAndUserBind(
 		return nil, err
 	}
 	if len(sr.Entries) != 1 {
+		logging.WithFields("entries", len(sr.Entries)).Info("ldap: no single user found")
 		return nil, ErrNoSingleUser
 	}
 
 	user := sr.Entries[0]
 	// Bind as the user to verify their password
 	if err = conn.Bind(user.DN, password); err != nil {
+		logging.WithFields("userDN", user.DN).WithError(err).Info("ldap user bind failed")
 		return nil, ErrFailedLogin
 	}
 	return user, nil