add: foreign key support in database

add: more tests
fix: bad tag handling when finding 0 in column

include/helpers.h

@@ -8,24 +8,6 @@
 int
 helper_connect_tcp_server(char* host, uint16_t port);
 
-int
-helper_bind_tcp_server(char* addr, uint16_t port, int max_client_backlog);
-
-uint16_t
-helper_get_port(int sock);
-
-/**
- * @brief Open socket for discovery
- *
- * Will exit program when unable to open socket.
- *
- * @param discovery_port Port number to listen on for discovery broadcasts
- *
- * @return Open socket to accept discovery broadcasts on
- */
-int
-helper_open_discovery_socket(uint16_t discovery_port);
-
 void
 helper_parse_cli(int argc, const char **argv, config_t *config);