feat: Global 2FA enforcement (#8753)

resolves #8549

This PR add a config to enforce 2FA for the whole Forgejo instance. It can be configured to `none`, `admin` or `all`.
A user who is required to enable 2FA is like a disabled user. He can only see the `/user/settings/security`-Page to enable 2FA, this should be similar to a user which needs to change his password. Also api and git-commands are not allowed.

## Checklist

The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).

### Tests

- I added test coverage for Go changes...
  - [x] in their respective `*_test.go` for unit tests.
  - [x] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I added test coverage for JavaScript changes...
  - [ ] in `web_src/js/*.test.js` if it can be unit tested.
  - [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [ ] I did not document these changes and I do not expect someone else to do it.

I will do it, if the general idea of this PR is a good feature.

### Release notes

- [ ] I do not want this change to show in the release notes.
- [x] I want the title to show in the release notes with a link to this pull request.
- [ ] I want the content of the `release-notes/<pull request number>.md` to be be used for the release notes instead of the title.

<!--start release-notes-assistant-->

## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Security features
  - [PR](https://codeberg.org/forgejo/forgejo/pulls/8753): <!--number 8753 --><!--line 0 --><!--description R2xvYmFsIDJGQSBlbmZvcmNlbWVudA==-->Global 2FA enforcement<!--description-->
<!--end release-notes-assistant-->

Co-authored-by: 0ko <0ko@noreply.codeberg.org>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8753
Reviewed-by: 0ko <0ko@noreply.codeberg.org>
Reviewed-by: Ellen Εμιλία Άννα Zscheile <fogti@noreply.codeberg.org>
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: zokki <zokki.softwareschmiede@gmail.com>
Co-committed-by: zokki <zokki.softwareschmiede@gmail.com>

routers/web/home.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"strconv"
 
+	auth_model "forgejo.org/models/auth"
 	"forgejo.org/models/db"
 	repo_model "forgejo.org/models/repo"
 	user_model "forgejo.org/models/user"
@@ -35,18 +36,37 @@ func Home(ctx *context.Context) {
 		if !ctx.Doer.IsActive && setting.Service.RegisterEmailConfirm {
 			ctx.Data["Title"] = ctx.Tr("auth.active_your_account")
 			ctx.HTML(http.StatusOK, auth.TplActivate)
-		} else if !ctx.Doer.IsActive || ctx.Doer.ProhibitLogin {
+			return
+		}
+		if !ctx.Doer.IsActive || ctx.Doer.ProhibitLogin {
 			log.Info("Failed authentication attempt for %s from %s", ctx.Doer.Name, ctx.RemoteAddr())
 			ctx.Data["Title"] = ctx.Tr("auth.prohibit_login")
 			ctx.HTML(http.StatusOK, "user/auth/prohibit_login")
-		} else if ctx.Doer.MustChangePassword {
+			return
+		}
+		if ctx.Doer.MustChangePassword {
 			ctx.Data["Title"] = ctx.Tr("auth.must_change_password")
 			ctx.Data["ChangePasscodeLink"] = setting.AppSubURL + "/user/change_password"
 			middleware.SetRedirectToCookie(ctx.Resp, setting.AppSubURL+ctx.Req.URL.RequestURI())
 			ctx.Redirect(setting.AppSubURL + "/user/settings/change_password")
-		} else {
-			user.Dashboard(ctx)
+			return
 		}
+		if ctx.Doer.MustHaveTwoFactor() {
+			hasTwoFactor, err := auth_model.HasTwoFactorByUID(ctx, ctx.Doer.ID)
+			if err != nil {
+				ctx.Data["Title"] = ctx.Tr("auth.prohibit_login")
+				log.Error("Error getting 2fa: %s", err)
+				ctx.Error(http.StatusInternalServerError, "HasTwoFactorByUID", err.Error())
+				return
+			}
+			if !hasTwoFactor {
+				ctx.Data["Title"] = ctx.Tr("auth.prohibit_login")
+				ctx.Redirect(setting.AppSubURL + "/user/settings/security")
+				return
+			}
+		}
+
+		user.Dashboard(ctx)
 		return
 		// Check non-logged users landing page.
 	} else if setting.LandingPageURL != setting.LandingPageHome {