migrations: add migrations for module compatibility sorting

Add the "incompatible" column to both the modules and
module_version_states tables in order to sort modules by compatibility
whenever they are being displayed or processed.

Updates golang/go#37714

Change-Id: I1f7b5dd55563b38af5c54a692b5e70512ef24c0e
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/247404
Run-TryBot: Julie Qiu <julie@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Julie Qiu <julie@golang.org>

migrations/000025_add_module_incomapatible_column.down.sql

@@ -0,0 +1,10 @@
+-- Copyright 2020 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 incompatible;
+ALTER TABLE module_version_states DROP COLUMN incompatible;
+
+END;

migrations/000025_add_module_incomapatible_column.up.sql

@@ -0,0 +1,23 @@
+-- Copyright 2020 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 incompatible boolean;
+ALTER TABLE module_version_states ADD COLUMN incompatible boolean;
+
+COMMENT ON COLUMN modules.incompatible IS
+'COLUMN incompatible defines whether the the version for the given module is incompatible';
+COMMENT ON COLUMN module_version_states.incompatible IS
+'COLUMN incompatible defines whether the the version for the given module is incompatible';
+
+CREATE INDEX idx_modules_incompatible on modules (incompatible);
+COMMENT ON INDEX idx_modules_incompatible IS
+'INDEX idx_modules_incompatible is used to sort versions if they are incompatible';
+
+CREATE INDEX idx_module_version_states_incompatible on module_version_states (incompatible);
+COMMENT ON INDEX idx_module_version_states_incompatible IS
+'INDEX idx_module_version_states_incompatible is used to sort versions if they are incompatible';
+
+END;