Add user blocking

- Add the ability to block a user via their profile page.
- This will unstar their repositories and visa versa.
- Blocked users cannot create issues or pull requests on your the doer's repositories (mind that this is not the case for organizations).
- Blocked users cannot comment on the doer's opened issues or pull requests.
- Blocked users cannot add reactions to doer's comments.
- Blocked users cannot cause a notification trough mentioning the doer.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/540

routers/api/v1/repo/issue_comment.go

@@ -364,7 +364,11 @@ func CreateIssueComment(ctx *context.APIContext) {
 
 	comment, err := issue_service.CreateIssueComment(ctx, ctx.Doer, ctx.Repo.Repository, issue, form.Body, nil)
 	if err != nil {
-		ctx.Error(http.StatusInternalServerError, "CreateIssueComment", err)
+		if errors.Is(err, user_model.ErrBlockedByUser) {
+			ctx.Error(http.StatusForbidden, "CreateIssueComment", err)
+		} else {
+			ctx.Error(http.StatusInternalServerError, "CreateIssueComment", err)
+		}
 		return
 	}