[NO ISSUE][EXT] Add NullableDecl interface

- user model changes: no
- storage format changes: no
- interface changes: added NullableDecl interface

Change-Id: I42f01b80892b3d1d7a4125bc1efab004126d2150
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb/+/16525
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Michael Blow <mblow@apache.org>
diff --git a/asterixdb/asterix-external-data/src/main/java/org/checkerframework/checker/nullness/compatqual/NullableDecl.java b/asterixdb/asterix-external-data/src/main/java/org/checkerframework/checker/nullness/compatqual/NullableDecl.java
new file mode 100644
index 0000000..a4cb401
--- /dev/null
+++ b/asterixdb/asterix-external-data/src/main/java/org/checkerframework/checker/nullness/compatqual/NullableDecl.java
@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.checkerframework.checker.nullness.compatqual;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/*
+ * This is a clean room implementation of the NullableDecl interface based
+ * on 3 requirements:
+ * 1. shall be an @interface named NullableDecl
+ * 2. shall be in the org.checkerframework.checker.nullness.compatqual package
+ * 3. the rention policy for the interface shall be RUNTIME
+ */
+@Retention(RetentionPolicy.RUNTIME)
+public @interface NullableDecl {
+}