[feature] implement custom_emojis endpoint (#563)

* implement custom_emojis api endpoint

* add tests for getting custom emoji out of the database and converting to api emoji

* change sort direction of emoji query

* change logging level and initialize array with known length as per kim's suggestions

* add continue to lessen risk of making a malformed struct during conversion from db to api emojis

internal/processing/media/getemoji.go

@@ -0,0 +1,50 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   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 media
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/sirupsen/logrus"
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+)
+
+func (p *processor) GetCustomEmojis(ctx context.Context) ([]*apimodel.Emoji, gtserror.WithCode) {
+	emojis, err := p.db.GetCustomEmojis(ctx)
+	if err != nil {
+		if err != db.ErrNoEntries {
+			return nil, gtserror.NewErrorNotFound(fmt.Errorf("db error retrieving custom emojis: %s", err))
+		}
+	}
+
+	apiEmojis := make([]*apimodel.Emoji, 0, len(emojis))
+	for _, gtsEmoji := range emojis {
+		apiEmoji, err := p.tc.EmojiToAPIEmoji(ctx, gtsEmoji)
+		if err != nil {
+			logrus.Errorf("error converting emoji with id %s: %s", gtsEmoji.ID, err)
+			continue
+		}
+		apiEmojis = append(apiEmojis, &apiEmoji)
+	}
+
+	return apiEmojis, nil
+}