string `INSERT INTO agents (agent_id, agent_type, runs_on_node_id, pmm_agent_id, node_id, service_id, disabled, status, created_at, updated_at, tls, tls_skip_verify, max_query_length, query_examples_disabled, comments_parsing_disabled, max_query_log_size, table_count_tablestats_group_limit, rds_basic_metrics_disabled, rds_enhanced_metrics_disabled, push_metrics, expose_exporter) ` has 4 occurrences, make it a constant (goconst)