fix(session): adds a compatablity for session (#14085)

Add compatibility to #13990

KM-878

Author: raoxiaoyan

kong/clustering/compat/removed_fields.lua

@@ -228,4 +228,10 @@ return {
       "queue.concurrency_limit",
     },
   },
+  [30010000000] = {
+    session = {
+      "hash_subject",
+      "store_metadata",
+    }
+  }
 }

spec/02-integration/09-hybrid_mode/09-config-compat_spec.lua

@@ -602,6 +602,31 @@ describe("CP/DP config compat transformations #" .. strategy, function()
       end)
     end)
 
+    describe("compatibility tests for sesssion plugin", function ()
+      it("removes `config.store_metadata` and `config.hash_subject` before sending them to older(3.9.0.0)DP nodes", function ()
+            local session = admin.plugins:insert {
+              name = "session",
+              enabled = true,
+              config = {
+                -- [[ new fields 3.10.0
+                store_metadata = true,
+                hash_subject = true,
+                -- ]]
+              }
+            }
+
+            assert.not_nil(session.config.store_metadata)
+            assert.not_nil(session.config.hash_subject)
+            local expected_session = cycle_aware_deep_copy(session)
+            expected_session.config.store_metadata = nil
+            expected_session.config.hash_subject = nil
+            do_assert(uuid(), "3.9.0", expected_session)
+
+            -- cleanup
+            admin.plugins:remove({ id = session.id })
+      end)
+    end)
+
     describe("ai plugins supported providers", function()
       it("[ai-proxy] tries to use unsupported providers on older Kong versions", function()
         -- [[ 3.8.x ]] --