[feature] Application creation + management via API + settings panel (#3906)

* [feature] Application creation + management via API + settings panel

* fix docs links

* add errnorows test

* use known application as shorter

* add comment about side effects

internal/processing/application/delete.go

@@ -0,0 +1,70 @@
+// 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 application
+
+import (
+	"context"
+	"errors"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+)
+
+func (p *Processor) Delete(
+	ctx context.Context,
+	userID string,
+	appID string,
+) (*apimodel.Application, gtserror.WithCode) {
+	app, err := p.state.DB.GetApplicationByID(ctx, appID)
+	if err != nil && !errors.Is(err, db.ErrNoEntries) {
+		err := gtserror.Newf("db error getting app %s: %w", appID, err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	if app == nil {
+		err := gtserror.Newf("app %s not found in the db", appID)
+		return nil, gtserror.NewErrorNotFound(err)
+	}
+
+	if app.ManagedByUserID != userID {
+		err := gtserror.Newf("app %s not managed by user %s", appID, userID)
+		return nil, gtserror.NewErrorNotFound(err)
+	}
+
+	// Convert app before deletion.
+	apiApp, err := p.converter.AppToAPIAppSensitive(ctx, app)
+	if err != nil {
+		err := gtserror.Newf("error converting app to api app: %w", err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	// Delete app itself.
+	if err := p.state.DB.DeleteApplicationByID(ctx, appID); err != nil {
+		err := gtserror.Newf("db error deleting app %s: %w", appID, err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	// Delete all tokens owned by app.
+	if err := p.state.DB.DeleteTokensByClientID(ctx, app.ClientID); err != nil {
+		err := gtserror.Newf("db error deleting tokens for app %s: %w", appID, err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	return apiApp, nil
+}