[feature] Hashtag federation (in/out), hashtag client API endpoints (#2032)

* update go-fed

* do the things

* remove unused columns from tags

* update to latest lingo from main

* further tag shenanigans

* serve stub page at tag endpoint

* we did it lads

* tests, oh tests, ohhh tests, oh tests (doo doo doo doo)

* swagger docs

* document hashtag usage + federation

* instanceGet

* don't bother parsing tag href

* rename whereStartsWith -> whereStartsLike

* remove GetOrCreateTag

* dont cache status tag timelineability

1 files changed, 60 insertions, 0 deletions

diff --git a/internal/visibility/tag_timeline.go b/internal/visibility/tag_timeline.go
new file mode 100644
index 000000000..b2c9dbf29
--- /dev/null
+++ b/internal/visibility/tag_timeline.go
@@ -0,0 +1,60 @@
+// 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 visibility
+
+import (
+	"context"
+	"time"
+
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+)
+
+// StatusHomeTimelineable checks if given status should be included
+// on requester's tag timeline, primarily relying on status visibility
+// to requester and the AP visibility setting.
+func (f *Filter) StatusTagTimelineable(
+	ctx context.Context,
+	requester *gtsmodel.Account,
+	status *gtsmodel.Status,
+) (bool, error) {
+	if status.CreatedAt.After(time.Now().Add(24 * time.Hour)) {
+		// Statuses made over 1 day in the future we don't show...
+		log.Warnf(ctx, "status >24hrs in the future: %+v", status)
+		return false, nil
+	}
+
+	// Don't show boosts on tag timeline.
+	if status.BoostOfID != "" {
+		return false, nil
+	}
+
+	// Check whether status is visible to requesting account.
+	visible, err := f.StatusVisible(ctx, requester, status)
+	if err != nil {
+		return false, err
+	}
+
+	if !visible {
+		log.Trace(ctx, "status not visible to timeline requester")
+		return false, nil
+	}
+
+	// Looks good!
+	return true, nil
+}