introduce lookup of subscribers based on their extension number

diff --git a/src/db.c b/src/db.c
index 50459cf..b538d5d 100644
--- a/src/db.c
+++ b/src/db.c
@@ -119,6 +119,7 @@
 		"id INTEGER PRIMARY KEY AUTOINCREMENT, "
 		"created TIMESTAMP NOT NULL, "
 		"updated TIMESTAMP NOT NULL, "
+		"name TEXT, "
 		"imei NUMERIC UNIQUE NOT NULL"
 		")"
 	);
@@ -219,6 +220,15 @@
 		);
 		free(quoted);
 		break;
+	case GSM_SUBSCRIBER_EXTENSION:
+		dbi_conn_quote_string_copy(conn, id, &quoted);
+		result = dbi_conn_queryf(conn,
+			"SELECT * FROM Subscriber "
+			"WHERE extension = %s ",
+			quoted
+		);
+		free(quoted);
+		break;
 	default:
 		printf("DB: Unknown query selector for Subscriber.\n");
 		return NULL;