[MODERATION] add user blocking API

- Follow up for: #540, #802
- Add API routes for user blocking from user and organization
perspective.
- The new routes have integration testing.
- The new model functions have unit tests.
- Actually quite boring to write and to read this pull request.

(cherry picked from commit f3afaf15c7)
(cherry picked from commit 6d754db3e5)
(cherry picked from commit d0fc8bc9d3)
(cherry picked from commit 9a53b0d1a0)
(cherry picked from commit 44a2a4fd48)
(cherry picked from commit 182025db9c)
(cherry picked from commit 558a35963e)

routers/api/v1/utils/block.go

@@ -0,0 +1,65 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package utils
+
+import (
+	"net/http"
+
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/context"
+	api "code.gitea.io/gitea/modules/structs"
+	user_service "code.gitea.io/gitea/services/user"
+)
+
+// ListUserBlockedUsers lists the blocked users of the provided doer.
+func ListUserBlockedUsers(ctx *context.APIContext, doer *user_model.User) {
+	count, err := user_model.CountBlockedUsers(ctx, doer.ID)
+	if err != nil {
+		ctx.InternalServerError(err)
+		return
+	}
+
+	blockedUsers, err := user_model.ListBlockedUsers(ctx, doer.ID, GetListOptions(ctx))
+	if err != nil {
+		ctx.InternalServerError(err)
+		return
+	}
+
+	apiBlockedUsers := make([]*api.BlockedUser, len(blockedUsers))
+	for i, blockedUser := range blockedUsers {
+		apiBlockedUsers[i] = &api.BlockedUser{
+			BlockID: blockedUser.ID,
+			Created: blockedUser.CreatedUnix.AsTime(),
+		}
+		if err != nil {
+			ctx.InternalServerError(err)
+			return
+		}
+	}
+
+	ctx.SetTotalCountHeader(count)
+	ctx.JSON(http.StatusOK, apiBlockedUsers)
+}
+
+// BlockUser blocks the blockUser from the doer.
+func BlockUser(ctx *context.APIContext, doer, blockUser *user_model.User) {
+	err := user_service.BlockUser(ctx, doer.ID, blockUser.ID)
+	if err != nil {
+		ctx.InternalServerError(err)
+		return
+	}
+
+	ctx.Status(http.StatusNoContent)
+}
+
+// UnblockUser unblocks the blockUser from the doer.
+func UnblockUser(ctx *context.APIContext, doer, blockUser *user_model.User) {
+	err := user_model.UnblockUser(ctx, doer.ID, blockUser.ID)
+	if err != nil {
+		ctx.InternalServerError(err)
+		return
+	}
+
+	ctx.Status(http.StatusNoContent)
+}