[feature] Implement Web Push notification policy (#3721)

* Web Push: add policy column to subscriptions

* Web Push: add policy to API

* Web Push: test notification policy

* go-fmt unrelated file (how did this get thru?)

internal/db/bundb/migrations/20250131184755_add_web_push_subscription_policy.go

@@ -0,0 +1,83 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package migrations
+
+import (
+	"context"
+	"reflect"
+	"strings"
+
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/uptrace/bun"
+	"github.com/uptrace/bun/dialect"
+)
+
+func init() {
+	up := func(ctx context.Context, db *bun.DB) error {
+		return db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+			model := &gtsmodel.WebPushSubscription{}
+
+			// Get the column definition for the new policy column.
+			modelType := reflect.TypeOf(model)
+			columnDef, err := getBunColumnDef(tx, modelType, "Policy")
+			if err != nil {
+				return err
+			}
+
+			// Add the policy column.
+			switch tx.Dialect().Name() {
+			case dialect.SQLite:
+				// Doesn't support Bun feature AlterColumnExists.
+				if _, err = tx.
+					NewAddColumn().
+					Model(model).
+					ColumnExpr(columnDef).
+					Exec(ctx); // nocollapse
+				err != nil && !strings.Contains(err.Error(), "duplicate column name") {
+					// Return errors that aren't about this column already existing.
+					return err
+				}
+
+			case dialect.PG:
+				// Supports Bun feature AlterColumnExists.
+				if _, err = tx.
+					NewAddColumn().
+					Model(model).
+					ColumnExpr(columnDef).
+					IfNotExists().
+					Exec(ctx); // nocollapse
+				err != nil {
+					return err
+				}
+
+			default:
+				panic("unsupported db type")
+			}
+
+			return nil
+		})
+	}
+
+	down := func(ctx context.Context, db *bun.DB) error {
+		return nil
+	}
+
+	if err := Migrations.Register(up, down); err != nil {
+		panic(err)
+	}
+}