feat: switch migration language to SQL instead of Lua

src/traft/rpc/migration.rs

 pub mod apply {
     use crate::traft::{error::Error, node, rpc::sync, RaftIndex, RaftTerm, Result};
     use std::time::Duration;
+    use tarantool::{lua_state, tlua::LuaError};
 
     crate::define_rpc_request! {
         fn proc_apply_migration(req: Request) -> Result<Response> {
@@ -12,9 +13,9 @@ pub mod apply {
 
             match storage.migrations.get(req.migration_id)? {
                 Some(migration) => {
-                    match crate::tarantool::exec(migration.body.as_str()) {
+                    match lua_state().exec_with("box.execute(...)", migration.body) {
                         Ok(_) => Ok(Response{}),
-                        Err(e) => Err(e.into())
+                        Err(e) => Err(LuaError::from(e).into()),
                     }
                 }
                 None => Err(Error::other(format!("Migration {0} not found", req.migration_id))),

test/int/test_migration.py

@@ -31,22 +31,22 @@ def test_apply_migrations(cluster: Cluster):
     i1, _, _ = cluster.instances
     i1.promote_or_fail()
     i1.assert_raft_status("Leader")
+
     i1.call(
         "picolib.add_migration",
         1,
         """
-        box.schema.space.create('test_space', {
-            format = {
-                {name = 'id', type = 'unsigned'},
-                {name = 'value', type = 'string'},
-            }
-        })
-        """,
+    CREATE TABLE "test_space" (
+        "id" INT PRIMARY KEY
+    )""",
     )
     i1.call(
         "picolib.add_migration",
         2,
-        "box.space.test_space:create_index('pk', {parts = {'id'}})",
+        """
+    ALTER TABLE "test_space"
+    ADD COLUMN "value" VARCHAR(100)
+    """,
     )
 
     i1.call("picolib.push_schema_version", 2)
@@ -56,11 +56,11 @@ def test_apply_migrations(cluster: Cluster):
         assert conn.insert("test_space", [1, "foo"])
 
     @funcy.retry(tries=30, timeout=0.2)  # type: ignore
-    def assert_replicaset_version(conn):
+    def assert_replicaset_version(conn, v):
         position = conn.schema.get_field("replicasets", "current_schema_version")["id"]
-        assert [2, 2, 2] == [tuple[position] for tuple in conn.select("replicasets")]
+        assert [v, v, v] == [tuple[position] for tuple in conn.select("replicasets")]
 
     for i in cluster.instances:
         with i.connect(timeout=1) as conn:
             assert_space_insert(conn)
-            assert_replicaset_version(conn)
+            assert_replicaset_version(conn, 2)