feat(sql): made DbInstances public for managing directly from Rust (#1381)

.changes/sql-public-db-instances.md

@@ -0,0 +1,5 @@
+---
+"sql": patch
+---
+
+Made `DbInstances` public for managing database instances directly from `Rust`.

plugins/sql/src/plugin.rs

@@ -87,7 +87,7 @@ fn path_mapper(mut app_path: PathBuf, connection_string: &str) -> String {
 }
 
 #[derive(Default)]
-struct DbInstances(Mutex<HashMap<String, Pool<Db>>>);
+pub struct DbInstances(pub Mutex<HashMap<String, Pool<Db>>>);
 
 struct Migrations(Mutex<HashMap<String, MigrationList>>);