migrations: add deprecated_comment column to modules table

Add a column to the modules table that will hold
the "Deprecated" comment from the go.mod file.

For golang/go#41321

Change-Id: I6bce20ef6a84d6e33ed60811945f90930ae25a09
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/290033
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>

migrations/000063_add_deprecated.down.sql

@@ -0,0 +1,9 @@
+-- Copyright 2021 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+ALTER TABLE modules DROP COLUMN deprecated_comment;
+
+END;

migrations/000063_add_deprecated.up.sql

@@ -0,0 +1,12 @@
+-- Copyright 2021 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+ALTER TABLE modules ADD COLUMN deprecated_comment TEXT;
+
+COMMENT ON COLUMN modules.deprecated_comment IS
+'COLUMN deprecated_comment holds the "Deprecated" comment from the go.mod file, if any.';
+
+END;