[feature] Fetch + display custom emoji in statuses from remote instances (#807)

* start implementing remote emoji fetcher

* update status where pk

* aaa

* tidy up a little

* check size limits for emojis

* thank you linter, i love you <3

* update swagger docs

* add emoji dereference test

* make emoji max sizes configurable

* normalize db.ErrAlreadyExists

internal/processing/status/util.go

@@ -234,8 +234,7 @@ func (p *processor) ProcessTags(ctx context.Context, form *apimodel.AdvancedStat
 	}
 	for _, tag := range gtsTags {
 		if err := p.db.Put(ctx, tag); err != nil {
-			var alreadyExistsError *db.ErrAlreadyExists
-			if !errors.As(err, &alreadyExistsError) {
+			if !errors.Is(err, db.ErrAlreadyExists) {
 				return fmt.Errorf("error putting tags in db: %s", err)
 			}
 		}