router: introduce name identification

This commit allows router to use named config identification.

Part of tarantool#426

@TarantoolBot document
Title: vshard: vshard.router.buckets_info shows name

When `identification_mode` is `name_as_key`, buckets_info()
also returns name of the replicas, where buckets are stored:

```
tarantool> vshard.router.buckets_info()
---
- - uuid: aaaaaaaa-0000-4000-a000-000000000000
    status: available_rw
    name: replica_1_a
```

test/router-luatest/router_test.lua

@@ -649,3 +649,47 @@ g.test_router_service_info = function(g)
     -- Restore everything back.
     vtest.router_cfg(g.router, global_cfg)
 end
+
+g.test_named_config_identification = function(g)
+    t.run_only_if(vutil.version_is_at_least(3, 0, 0, 'entrypoint', 0, 0))
+    local new_cfg_template = table.deepcopy(cfg_template)
+    new_cfg_template.identification_mode = 'name_as_key'
+    new_cfg_template.sharding['replicaset_1'] = new_cfg_template.sharding[1]
+    new_cfg_template.sharding['replicaset_2'] = new_cfg_template.sharding[2]
+    new_cfg_template.sharding[1] = nil
+    new_cfg_template.sharding[2] = nil
+    local new_global_cfg = vtest.config_new(new_cfg_template)
+
+    -- Set names, as they should be verified on connection.
+    g.replica_1_a:exec(function()
+        box.cfg{instance_name = 'replica_1_a', replicaset_name = 'replicaset_1'}
+    end)
+    g.replica_1_b:exec(function()
+        box.cfg{instance_name = 'replica_1_b', replicaset_name = 'replicaset_1'}
+    end)
+    g.replica_2_a:exec(function()
+        box.cfg{instance_name = 'replica_2_a', replicaset_name = 'replicaset_2'}
+    end)
+    g.replica_2_b:exec(function()
+        box.cfg{instance_name = 'replica_2_b', replicaset_name = 'replicaset_2'}
+    end)
+
+    vtest.cluster_cfg(g, new_global_cfg)
+    vtest.router_cfg(g.router, new_global_cfg)
+
+    local router = g.router
+    local res, err = router:exec(function()
+        -- buckets_info shows name, when name identification is used.
+        local _, err = ivshard.router.bucket_discovery(1)
+        ilt.assert_equals(err, nil)
+        ilt.assert_not_equals(ivshard.router.buckets_info()[1].name, nil)
+        -- just basic test
+        return ivshard.router.callrw(1, 'echo', {1}, {timeout = iwait_timeout})
+    end)
+    t.assert(not err, 'no error')
+    t.assert_equals(res, 1, 'good result')
+
+    -- Restore everything back.
+    vtest.cluster_cfg(g, global_cfg)
+    vtest.router_cfg(g.router, global_cfg)
+end

test/router/router.result

@@ -393,10 +393,10 @@ _ = vshard.router.bucket_discovery(3)
 vshard.router.buckets_info(0, 3)
 ---
 - - status: unknown
-  - uuid: <replicaset_2>
-    status: available_rw
-  - uuid: <replicaset_2>
-    status: available_rw
+  - status: available_rw
+    uuid: <replicaset_2>
+  - status: available_rw
+    uuid: <replicaset_2>
 ...
 _ = test_run:cmd('stop server storage_2_a')
 ---
@@ -422,10 +422,10 @@ util.check_error(vshard.router.call, 1, 'read', 'echo', {123})
 vshard.router.buckets_info(0, 3)
 ---
 - - status: unknown
-  - uuid: <replicaset_2>
-    status: available_ro
-  - uuid: <replicaset_2>
-    status: available_ro
+  - status: available_ro
+    uuid: <replicaset_2>
+  - status: available_ro
+    uuid: <replicaset_2>
 ...
 _ = test_run:cmd('start server storage_2_a')
 ---
@@ -1164,46 +1164,46 @@ buckets_info = vshard.router.buckets_info()
 ...
 buckets_info[1]
 ---
-- uuid: <replicaset_2>
-  status: available_rw
+- status: available_rw
+  uuid: <replicaset_2>
 ...
 buckets_info[1501]
 ---
-- uuid: <replicaset_1>
-  status: available_rw
+- status: available_rw
+  uuid: <replicaset_1>
 ...
 vshard.router.buckets_info(0, 3)
 ---
-- - uuid: <replicaset_2>
-    status: available_rw
-  - uuid: <replicaset_2>
-    status: available_rw
-  - uuid: <replicaset_2>
-    status: available_rw
+- - status: available_rw
+    uuid: <replicaset_2>
+  - status: available_rw
+    uuid: <replicaset_2>
+  - status: available_rw
+    uuid: <replicaset_2>
 ...
 vshard.router.buckets_info(1500, 3)
 ---
 - 1502:
-    uuid: <replicaset_1>
     status: available_rw
-  1503:
     uuid: <replicaset_1>
+  1503:
     status: available_rw
-  1501:
     uuid: <replicaset_1>
+  1501:
     status: available_rw
+    uuid: <replicaset_1>
 ...
 vshard.router.buckets_info(vshard.consts.DEFAULT_BUCKET_COUNT - 3)
 ---
 - 3000:
-    uuid: <replicaset_1>
     status: available_rw
-  2998:
     uuid: <replicaset_1>
+  2998:
     status: available_rw
-  2999:
     uuid: <replicaset_1>
+  2999:
     status: available_rw
+    uuid: <replicaset_1>
 ...
 util.check_error(vshard.router.buckets_info, '123')
 ---