Add user blocking (#29028)

Fixes #17453

This PR adds the abbility to block a user from a personal account or
organization to restrict how the blocked user can interact with the
blocker. The docs explain what's the consequence of blocking a user.

Screenshots:


![grafik](https://github.com/go-gitea/gitea/assets/1666336/4ed884f3-e06a-4862-afd3-3b8aa2488dc6)


![grafik](https://github.com/go-gitea/gitea/assets/1666336/ae6d4981-f252-4f50-a429-04f0f9f1cdf1)


![grafik](https://github.com/go-gitea/gitea/assets/1666336/ca153599-5b0f-4b4a-90fe-18bdfd6f0b6b)

---------

Co-authored-by: Lauris BH <lauris@nix.lv>

routers/web/shared/user/block.go

@@ -0,0 +1,76 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package user
+
+import (
+	"errors"
+
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/web"
+	"code.gitea.io/gitea/services/context"
+	"code.gitea.io/gitea/services/forms"
+	user_service "code.gitea.io/gitea/services/user"
+)
+
+func BlockedUsers(ctx *context.Context, blocker *user_model.User) {
+	blocks, _, err := user_model.FindBlockings(ctx, &user_model.FindBlockingOptions{
+		BlockerID: blocker.ID,
+	})
+	if err != nil {
+		ctx.ServerError("FindBlockings", err)
+		return
+	}
+	if err := user_model.BlockingList(blocks).LoadAttributes(ctx); err != nil {
+		ctx.ServerError("LoadAttributes", err)
+		return
+	}
+	ctx.Data["UserBlocks"] = blocks
+}
+
+func BlockedUsersPost(ctx *context.Context, blocker *user_model.User) {
+	form := web.GetForm(ctx).(*forms.BlockUserForm)
+	if ctx.HasError() {
+		ctx.ServerError("FormValidation", nil)
+		return
+	}
+
+	blockee, err := user_model.GetUserByName(ctx, form.Blockee)
+	if err != nil {
+		ctx.ServerError("GetUserByName", nil)
+		return
+	}
+
+	switch form.Action {
+	case "block":
+		if err := user_service.BlockUser(ctx, ctx.Doer, blocker, blockee, form.Note); err != nil {
+			if errors.Is(err, user_model.ErrCanNotBlock) || errors.Is(err, user_model.ErrBlockOrganization) {
+				ctx.Flash.Error(ctx.Tr("user.block.block.failure", err.Error()))
+			} else {
+				ctx.ServerError("BlockUser", err)
+				return
+			}
+		}
+	case "unblock":
+		if err := user_service.UnblockUser(ctx, ctx.Doer, blocker, blockee); err != nil {
+			if errors.Is(err, user_model.ErrCanNotUnblock) || errors.Is(err, user_model.ErrBlockOrganization) {
+				ctx.Flash.Error(ctx.Tr("user.block.unblock.failure", err.Error()))
+			} else {
+				ctx.ServerError("UnblockUser", err)
+				return
+			}
+		}
+	case "note":
+		block, err := user_model.GetBlocking(ctx, blocker.ID, blockee.ID)
+		if err != nil {
+			ctx.ServerError("GetBlocking", err)
+			return
+		}
+		if block != nil {
+			if err := user_model.UpdateBlockingNote(ctx, block.ID, form.Note); err != nil {
+				ctx.ServerError("UpdateBlockingNote", err)
+				return
+			}
+		}
+	}
+}