Add API for changing Avatars (#25369)

This adds an API for uploading and Deleting Avatars for of Users, Repos
and Organisations. I'm not sure, if this should also be added to the
Admin API.

Resolves #25344

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Giteabot <teabot@gitea.io>

routers/api/v1/user/avatar.go

@@ -0,0 +1,63 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package user
+
+import (
+	"encoding/base64"
+	"net/http"
+
+	"code.gitea.io/gitea/modules/context"
+	api "code.gitea.io/gitea/modules/structs"
+	"code.gitea.io/gitea/modules/web"
+	user_service "code.gitea.io/gitea/services/user"
+)
+
+// UpdateAvatar updates the Avatar of an User
+func UpdateAvatar(ctx *context.APIContext) {
+	// swagger:operation POST /user/avatar user userUpdateAvatar
+	// ---
+	// summary: Update Avatar
+	// produces:
+	// - application/json
+	// parameters:
+	// - name: body
+	//   in: body
+	//   schema:
+	//     "$ref": "#/definitions/UpdateUserAvatarOption"
+	// responses:
+	//   "204":
+	//     "$ref": "#/responses/empty"
+	form := web.GetForm(ctx).(*api.UpdateUserAvatarOption)
+
+	content, err := base64.StdEncoding.DecodeString(form.Image)
+	if err != nil {
+		ctx.Error(http.StatusBadRequest, "DecodeImage", err)
+		return
+	}
+
+	err = user_service.UploadAvatar(ctx.Doer, content)
+	if err != nil {
+		ctx.Error(http.StatusInternalServerError, "UploadAvatar", err)
+	}
+
+	ctx.Status(http.StatusNoContent)
+}
+
+// DeleteAvatar deletes the Avatar of an User
+func DeleteAvatar(ctx *context.APIContext) {
+	// swagger:operation DELETE /user/avatar user userDeleteAvatar
+	// ---
+	// summary: Delete Avatar
+	// produces:
+	// - application/json
+	// responses:
+	//   "204":
+	//     "$ref": "#/responses/empty"
+	err := user_service.DeleteAvatar(ctx.Doer)
+	if err != nil {
+		ctx.Error(http.StatusInternalServerError, "DeleteAvatar", err)
+	}
+
+	ctx.Status(http.StatusNoContent)
+}