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>

services/issue/commit.go

@@ -5,6 +5,7 @@ package issue
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"html"
 	"net/url"
@@ -160,6 +161,9 @@ func UpdateIssuesCommit(ctx context.Context, doer *user_model.User, repo *repo_m
 
 			message := fmt.Sprintf(`<a href="%s/commit/%s">%s</a>`, html.EscapeString(repo.Link()), html.EscapeString(url.PathEscape(c.Sha1)), html.EscapeString(strings.SplitN(c.Message, "\n", 2)[0]))
 			if err = CreateRefComment(ctx, doer, refRepo, refIssue, message, c.Sha1); err != nil {
+				if errors.Is(err, user_model.ErrBlockedUser) {
+					continue
+				}
 				return err
 			}