[feature] Custom emoji updates (serve emoji via s2s api, tune db models) (#805)

* migrate emojis

* add get emoji to s2s (federation) API

* add new emoji db + cache functions

* add shortcodeDomain lookup for emojis

* check existing emojis w/cache, not w/constraints

* go fmt

* add putEmoji func

* use new db emoji funcs instead of where

* remove emojistringstotags func

* add unique constraint back in

* fix up broken migration

* update index

internal/api/s2s/emoji/emojiget.go

@@ -0,0 +1,74 @@
+/*
+   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 emoji
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+	"github.com/superseriousbusiness/gotosocial/internal/ap"
+	"github.com/superseriousbusiness/gotosocial/internal/api"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+)
+
+// EmojiGetHandler
+func (m *Module) EmojiGetHandler(c *gin.Context) {
+	// usernames on our instance are always lowercase
+	requestedEmojiID := strings.ToUpper(c.Param(EmojiIDKey))
+	if requestedEmojiID == "" {
+		err := errors.New("no emoji id specified in request")
+		api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGet)
+		return
+	}
+
+	format, err := api.NegotiateAccept(c, api.ActivityPubAcceptHeaders...)
+	if err != nil {
+		api.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGet)
+		return
+	}
+
+	ctx := c.Request.Context()
+	verifier, signed := c.Get(string(ap.ContextRequestingPublicKeyVerifier))
+	if signed {
+		ctx = context.WithValue(ctx, ap.ContextRequestingPublicKeyVerifier, verifier)
+	}
+
+	signature, signed := c.Get(string(ap.ContextRequestingPublicKeySignature))
+	if signed {
+		ctx = context.WithValue(ctx, ap.ContextRequestingPublicKeySignature, signature)
+	}
+
+	resp, errWithCode := m.processor.GetFediEmoji(ctx, requestedEmojiID, c.Request.URL)
+	if errWithCode != nil {
+		api.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
+		return
+	}
+
+	b, err := json.Marshal(resp)
+	if err != nil {
+		api.ErrorHandler(c, gtserror.NewErrorInternalError(err), m.processor.InstanceGet)
+		return
+	}
+
+	c.Data(http.StatusOK, format, b)
+}